Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on March 15, 2016, 12:19:54 PM
Post by: AT8 Cat on March 15, 2016, 12:19:54 PM
Hey guys,
I'm looking for some input and help to figure out what I need to do to correct my speedo after I get a set of 3.73 gears installed on my 1988 Cougar XR7 5.0L auto with 8.8 trak-lok rear end. Car currently has factory 3.08 gears and has mechanical gauges but does not use a speedo cable. There seems to be many types of driven gears and drive gears and I'm not sure how to proceed. Your help is appreciated. Thanks!
I'm looking for some input and help to figure out what I need to do to correct my speedo after I get a set of 3.73 gears installed on my 1988 Cougar XR7 5.0L auto with 8.8 trak-lok rear end. Car currently has factory 3.08 gears and has mechanical gauges but does not use a speedo cable. There seems to be many types of driven gears and drive gears and I'm not sure how to proceed. Your help is appreciated. Thanks!
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: thunderjet302 on March 15, 2016, 03:18:28 PM
Post by: thunderjet302 on March 15, 2016, 03:18:28 PM
This gear: https://lmr.com/item/LRS-17271J-K/83-95-Mustang-23-Tooth-Speedo-Gear-Kit-Auto
I use it in my Thunderbird with 3.73 gears. Just pop the old one off the vehicle speed sensor and pop the 23 tooth gear on in its place.
I use it in my Thunderbird with 3.73 gears. Just pop the old one off the vehicle speed sensor and pop the 23 tooth gear on in its place.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: ZondaC12 on March 15, 2016, 04:38:59 PM
Post by: ZondaC12 on March 15, 2016, 04:38:59 PM
Wow. Nice ride sir!!!
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on March 15, 2016, 04:51:49 PM
Post by: AT8 Cat on March 15, 2016, 04:51:49 PM
Nice!! Sounds like it's worked well for you thunderjet302, so I'll order it up and put it in. Thanks for the tip and for the link for purchasing it. I'm looking forward to seeing what these 3.73's do for the car!!
[ATTACH=CONFIG]37313[/ATTACH]
[ATTACH=CONFIG]37313[/ATTACH]
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on March 15, 2016, 04:56:47 PM
Post by: AT8 Cat on March 15, 2016, 04:56:47 PM
Thank-you. You've got a nice Anni there Zondac12!
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: ZondaC12 on March 15, 2016, 06:45:36 PM
Post by: ZondaC12 on March 15, 2016, 06:45:36 PM
It's simply ridiculous sometimes, to even imagine one of these cars looking pretty this far north!
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: fast Ed on March 15, 2016, 10:39:40 PM
Post by: fast Ed on March 15, 2016, 10:39:40 PM
Whereabouts in Ontario are you? I live in Caledon, and am a parts guy at the dealer in Waterloo. Most of the speedo gears are still available to order from Ford at a reasonable price. Shoot me a p.m. if I can help.
That's a great looking cat, the Saleen style wheels look at home on there.
cheers
Ed
That's a great looking cat, the Saleen style wheels look at home on there.
cheers
Ed
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on March 16, 2016, 09:34:44 AM
Post by: AT8 Cat on March 16, 2016, 09:34:44 AM
Fast Ed, you've got a bit of a trek to get to work. I'm in Cambridge. When I was trying to figure out this speedo gear change last fall I found out that Ford only made up to a 21 tooth gear. According to ^thunderjet302^ I need a 23 tooth which I guess is only available through the aftermarket. And thanks for the compliment on the wheels, I was happy how they finished the car off nicely!
@ ZondaC12 - I know what you mean, in the last couple of years I've seen only one of these cars and it was very nice. Hard to find anymore. That should put the value of these up shouldn't it? LOL
@ ZondaC12 - I know what you mean, in the last couple of years I've seen only one of these cars and it was very nice. Hard to find anymore. That should put the value of these up shouldn't it? LOL
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: mcb82gt on March 16, 2016, 05:22:57 PM
Post by: mcb82gt on March 16, 2016, 05:22:57 PM
Mine is still a little off. I cant remember if I used the 21 or 23 tooth though, its been too long ago. LOL
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: fast Ed on March 18, 2016, 12:00:33 AM
Post by: fast Ed on March 18, 2016, 12:00:33 AM
The "aftermarket" 23 tooth speedo gears are just a Jeep part, you can order one from the Chrysler dealer as part number J3167393. The issue with the 23 tooth version is that the teeth are very fine because of trying to fit so many on such a small plastic gear ... many people experience premature wear on them. Upside is, not a lot of money to replace one if it does happen.
cheers
Ed
cheers
Ed
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: TurboCoupe50 on March 18, 2016, 09:51:33 AM
Post by: TurboCoupe50 on March 18, 2016, 09:51:33 AM
If trans has a 8 tooth gear cut into output shaft a 23 is required for 3.73, this is by far what most passenger car AOD trans have... The performance(Super Coupe) & truck versions have a 7 tooth output so 21 will match 3.73 using those trans...
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on March 19, 2016, 11:24:50 AM
Post by: AT8 Cat on March 19, 2016, 11:24:50 AM
I've heard conflicting stories about whether my '88 AOD is a 7 tooth or an 8 tooth drive. How do you know for certain, can you see the drive gear well enough through the VSS hole?
Also, if the 23 tooth gear does suffer premature wear does it mess up the "drive" gear as well?
Also, if the 23 tooth gear does suffer premature wear does it mess up the "drive" gear as well?
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: 88Merc50 on March 25, 2016, 07:50:34 PM
Post by: 88Merc50 on March 25, 2016, 07:50:34 PM
Wow NICE 88 xr7, just like mine except mine has the side stripes.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: ISTLCRUZ on March 27, 2016, 07:05:12 AM
Post by: ISTLCRUZ on March 27, 2016, 07:05:12 AM
Quote from: AT8 Cat;454392
I've heard conflicting stories about whether my '88 AOD is a 7 tooth or an 8 tooth drive. How do you know for certain, can you see the drive gear well enough through the VSS hole?
Also, if the 23 tooth gear does suffer premature wear does it mess up the "drive" gear as well?
Following your thread as I need to order a new gear as well.( just swapped in a 3.55 TC rear axle) What did you decide on your AOD? 7 tooth or 8? I have an 87 5.0 Bird with AOD. TurboCoupe 50 said MOST came with 8 tooth so I may get mine tomorrow. Ray
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: Moonmount on March 27, 2016, 07:35:09 PM
Post by: Moonmount on March 27, 2016, 07:35:09 PM
Could you post some more pics of that car its gorgeous also where did you get those sc wheels and how well do they fit?
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: JeremyB on March 28, 2016, 11:57:14 AM
Post by: JeremyB on March 28, 2016, 11:57:14 AM
Quote from: AT8 Cat;454392
I've heard conflicting stories about whether my '88 AOD is a 7 tooth or an 8 tooth drive. How do you know for certain, can you see the drive gear well enough through the VSS hole?
http://www.sccoa.com/faq/speedgr.html
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on March 29, 2016, 10:50:38 AM
Post by: AT8 Cat on March 29, 2016, 10:50:38 AM
Quote from: ISTLCRUZ;454506
Following your thread as I need to order a new gear as well.( just swapped in a 3.55 TC rear axle) What did you decide on your AOD? 7 tooth or 8? I have an 87 5.0 Bird with AOD. TurboCoupe 50 said MOST came with 8 tooth so I may get mine tomorrow. Ray
Sounds 99% like it'll be an 8 tooth in there so I will need a 23 tooth driven gear. I've heard guys on here with '87's that had an 8 tooth, but no one with an '88 has told me what they've got. Right now the car is still tucked away for winter but it will be out in a few weeks as soon as the weather warms up some more. I'll let you know what happens when the job is done.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on March 29, 2016, 10:57:41 AM
Post by: AT8 Cat on March 29, 2016, 10:57:41 AM
Quote from: Moonmount;454511
Could you post some more pics of that car its gorgeous also where did you get those sc wheels and how well do they fit?
Thanks!! I'll have to get some more pics on here when I get a chance to, but the wheels and tires came from americanmuscle.com and I would recommend them as the prices are good, quality is good, and delivery was very timely. These are SC replicas. I ordered 17X8 for the front with 245/45/17 Mickey Thompson tires, and 17x9 with 275/45/17 in the back with zero fitment problems. Any wider in the rear would probably have to remove the quad shocks but I didn't want to do that. American muscle does have a 10' wide rim as well.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: fast Ed on March 29, 2016, 09:54:52 PM
Post by: fast Ed on March 29, 2016, 09:54:52 PM
275/40 rear maybe? Don't think anyone is making a 275/45R17. 275/40 would match the overall diameter of the 245/45 fronts.
cheers
Ed
cheers
Ed
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: thunderjet302 on March 30, 2016, 01:55:57 PM
Post by: thunderjet302 on March 30, 2016, 01:55:57 PM
Quote from: AT8 Cat;454392
I've heard conflicting stories about whether my '88 AOD is a 7 tooth or an 8 tooth drive. How do you know for certain, can you see the drive gear well enough through the VSS hole?
Also, if the 23 tooth gear does suffer premature wear does it mess up the "drive" gear as well?
You have an 8 tooth drive gear. My 88 Thunderbird's AOD has an 8 tooth drive gear.
If the 23 tooth gear wears prematurely it will not damage the drive gear. The drive gear in the AOD is metal. The speedometer driven gear is plastic.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: mcb82gt on March 30, 2016, 09:05:58 PM
Post by: mcb82gt on March 30, 2016, 09:05:58 PM
Sparking my memory, I think I needed the 23 tooth, but went with the 21 tooth because it wasn't the aftermarket and would last longer. I'm about 5 mph off at around 60/65 MPH.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on March 31, 2016, 12:08:33 PM
Post by: AT8 Cat on March 31, 2016, 12:08:33 PM
Quote from: fast Ed;454549
275/40 rear maybe? Don't think anyone is making a 275/45R17. 275/40 would match the overall diameter of the 245/45 fronts.
cheers
Ed
My bad, you are correct sir! Thanks for the correction.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on March 31, 2016, 12:09:58 PM
Post by: AT8 Cat on March 31, 2016, 12:09:58 PM
Quote from: thunderjet302;454555
You have an 8 tooth drive gear. My 88 Thunderbird's AOD has an 8 tooth drive gear.
If the 23 tooth gear wears prematurely it will not damage the drive gear. The drive gear in the AOD is metal. The speedometer driven gear is plastic.
Awesome, that answers that. Thank you!
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: Moonmount on April 23, 2016, 10:56:19 PM
Post by: Moonmount on April 23, 2016, 10:56:19 PM
How well do you like the staggered setup does it induce alot of understeer?
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on April 25, 2016, 11:38:42 AM
Post by: AT8 Cat on April 25, 2016, 11:38:42 AM
Quote from: Moonmount;454990
How well do you like the staggered setup does it induce alot of understeer?
Seems good. I don't race it or anything but I have thrown it into some of the roundabouts here in town and it grips very good considering it's a mostly original 28 year old car. No understeer noted. These cars need the staggered set up to fill up the large rear wheel wells. I get a lot of compliments on these rims as they really finish off the look of the car nicely.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on April 25, 2016, 12:11:56 PM
Post by: AT8 Cat on April 25, 2016, 12:11:56 PM
**UPDATE** Finally got nice enough weather here to get the car out of hibernation and have the 3.73's installed. Job went well. Car now has a bit more "get up and go". On the highway, car used to rev around 2000 rpms at 115 kph, now it's 2000 rpms at about 100 kph.
I ordered a 23 tooth speedo gear from the local Jeep dealer as suggested by fast ed. It was an exact fit and since it's from another OEM dealer I'm hoping it's better quality than the aftermarket 23 tooth that was also available. However, according to my GPS with the 23 tooth gear I'm off by about 7 kph less than what the speedo reads. Do I need another gear or is that as good as it's going to get with the limited amount of gears available? I did the math, and like many suggested on this thread we come up with 23 tooth. How can we be off by 7 kph? This is my first gear swap so I'm a little stumped.
I ordered a 23 tooth speedo gear from the local Jeep dealer as suggested by fast ed. It was an exact fit and since it's from another OEM dealer I'm hoping it's better quality than the aftermarket 23 tooth that was also available. However, according to my GPS with the 23 tooth gear I'm off by about 7 kph less than what the speedo reads. Do I need another gear or is that as good as it's going to get with the limited amount of gears available? I did the math, and like many suggested on this thread we come up with 23 tooth. How can we be off by 7 kph? This is my first gear swap so I'm a little stumped.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: Haystack on April 25, 2016, 05:00:54 PM
Post by: Haystack on April 25, 2016, 05:00:54 PM
What's size tires are you running? 7kph is only about 4mph off.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on April 26, 2016, 09:15:23 AM
Post by: AT8 Cat on April 26, 2016, 09:15:23 AM
Quote from: Haystack;455011
What's size tires are you running? 7kph is only about 4mph off.
Rear tires are 275/40R17.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: fast Ed on May 01, 2016, 10:55:20 AM
Post by: fast Ed on May 01, 2016, 10:55:20 AM
It's still reading too high? If so, that it as close as it gets, no higher tooth count than 23 on the speedo gears (that I'm aware of).
cheers
Ed
cheers
Ed
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: Aerocoupe on May 01, 2016, 08:13:36 PM
Post by: Aerocoupe on May 01, 2016, 08:13:36 PM
Pull the AOD and put a T-5 in there with a black 6 tooth drive gear and that will solve the problem. I am kidding but it sure sucks that you have to replace the whole shaft on the AOD's to change the drive gear.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: TurboCoupe50 on May 01, 2016, 09:39:50 PM
Post by: TurboCoupe50 on May 01, 2016, 09:39:50 PM
Quote from: AT8 Cat;455008
**UPDATE** Finally got nice enough weather here to get the car out of hibernation and have the 3.73's installed. Job went well. Car now has a bit more "get up and go". On the highway, car used to rev around 2000 rpms at 115 kph, now it's 2000 rpms at about 100 kph.
I ordered a 23 tooth speedo gear from the local Jeep dealer as suggested by fast ed. It was an exact fit and since it's from another OEM dealer I'm hoping it's better quality than the aftermarket 23 tooth that was also available. However, according to my GPS with the 23 tooth gear I'm off by about 7 kph less than what the speedo reads. Do I need another gear or is that as good as it's going to get with the limited amount of gears available? I did the math, and like many suggested on this thread we come up with 23 tooth. How can we be off by 7 kph? This is my first gear swap so I'm a little stumped.
Meaning you need a gear with more teeth... Speedo shops can install a external drive that would correct reading... Used to be OEM on vehicles that had like 4.11 & 4.30 cogs from factory...
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: Aerocoupe on May 02, 2016, 10:07:45 AM
Post by: Aerocoupe on May 02, 2016, 10:07:45 AM
When I changed from an T-5 to the Tremec TKO in my Bird and upped the exhaust to 3-1/2" to the lers the area where the speedo cable connected to the sensor assembly (http://www.americanmuscle.com/pyi-speedsensor-8793.html) got really small and the speedo cable would not turn a 90 quick enough to get it to connect to the sensor assembly and clear the exhaust, cross memeber, and sheet metal. I ended up buying a 90 degree adapter which has a built in ratio adapter to solve the problem. Mine is like the one this page http://www.partshp.com/speedometer_gears.htm so scroll down until you see #43. The only problem is that I also had to get a new speedo cable as the speedo cable attachment point is threaded which I believe was like P/N 6800 on the previously mentioned website. This is not a cheap solution but in your case most likely cheaper that pulling the AOD and swapping the out put shaft if that will even correct the issue.
Mine will be coming out shortly as I am swapping over to AutoMeter gauges and the speedo is electric so I can go back to the original sensor assembly and then calibrate the speedo. This is months down the road or I would offer my setup to you.
Mine will be coming out shortly as I am swapping over to AutoMeter gauges and the speedo is electric so I can go back to the original sensor assembly and then calibrate the speedo. This is months down the road or I would offer my setup to you.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: JeremyB on May 02, 2016, 04:36:45 PM
Post by: JeremyB on May 02, 2016, 04:36:45 PM
This page explains how you figure out what driven gear you need for the VSS.
http://www.accutach.com/calculators/ford-vss-calculator
Basically, the ECU is looking for 8000 pulses per mile from the VSS.
To calculate pulses per mile:
Tire rev/mile * Rear End Ratio * VSS gear ratio * VSS reluctor pulses per revolution = VSS (pulses per mile)
For your stock setup...
Tire rev/mile, P215/70/R14 = 811 (See http://www.1010tires.com/Tools/Tire-Size-Calculator)
Rear End Ratio = 3.08
VSS Gear Ratio (drive/driven) = 8/20 = 0.4
VSS reluctor pulses per revolution = 8 (Constant for all Ford VSS)
So,
811 * 3.08 * .4 * 8 = 7993 pulses/mile. The ECU is expecting 8000, so you have an error of 0.08% Completely negligible.
For your new setup:
Tire rev/mile, P215/70/R14 = 810 (See http://www.1010tires.com/Tools/Tire-Size-Calculator)
Rear End Ratio = 3.73
VSS Gear Ratio (drive/driven) = 8/23 = 0.3478
VSS reluctor pulses per revolution = 8 (Constant for all Ford VSS)
810 * 3.73 * 0.3478 * 8 = 8407 pulses/mile. That's an error of 5.08% - which is what you should see with your present setup.
You'd need a 24.17 tooth driven gear to get a 'perfect' speedo output with your tires and rear end.
If you had a 7 tooth drive gear, you'd want a 21 tooth. (0.7% error)
6 tooth drive: you'd want a 18 tooth (0.7% error)
I think either the Speed-Cal (http://"https://www.dallasmustang.com/speed-cal-1994-2004-5-speed-cars.html")or Ford Racing speed-dial (http://"https://lmr.com/item/M4209ADPTAC/94-10-Mustang-Speed-Dial-Speedometer-Adjuster-M-4209ADPT-AC") will convert your 8407 pulses/min to the expected 8000 pulses/min. They run ~$100-130.
They specify 1994+ Mustangs because 1993 and previous Mustangs had mechanical cables.
http://www.accutach.com/calculators/ford-vss-calculator
Basically, the ECU is looking for 8000 pulses per mile from the VSS.
To calculate pulses per mile:
Tire rev/mile * Rear End Ratio * VSS gear ratio * VSS reluctor pulses per revolution = VSS (pulses per mile)
For your stock setup...
Tire rev/mile, P215/70/R14 = 811 (See http://www.1010tires.com/Tools/Tire-Size-Calculator)
Rear End Ratio = 3.08
VSS Gear Ratio (drive/driven) = 8/20 = 0.4
VSS reluctor pulses per revolution = 8 (Constant for all Ford VSS)
So,
811 * 3.08 * .4 * 8 = 7993 pulses/mile. The ECU is expecting 8000, so you have an error of 0.08% Completely negligible.
For your new setup:
Tire rev/mile, P215/70/R14 = 810 (See http://www.1010tires.com/Tools/Tire-Size-Calculator)
Rear End Ratio = 3.73
VSS Gear Ratio (drive/driven) = 8/23 = 0.3478
VSS reluctor pulses per revolution = 8 (Constant for all Ford VSS)
810 * 3.73 * 0.3478 * 8 = 8407 pulses/mile. That's an error of 5.08% - which is what you should see with your present setup.
You'd need a 24.17 tooth driven gear to get a 'perfect' speedo output with your tires and rear end.
If you had a 7 tooth drive gear, you'd want a 21 tooth. (0.7% error)
6 tooth drive: you'd want a 18 tooth (0.7% error)
I think either the Speed-Cal (http://"https://www.dallasmustang.com/speed-cal-1994-2004-5-speed-cars.html")or Ford Racing speed-dial (http://"https://lmr.com/item/M4209ADPTAC/94-10-Mustang-Speed-Dial-Speedometer-Adjuster-M-4209ADPT-AC") will convert your 8407 pulses/min to the expected 8000 pulses/min. They run ~$100-130.
They specify 1994+ Mustangs because 1993 and previous Mustangs had mechanical cables.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: Haystack on May 02, 2016, 04:43:07 PM
Post by: Haystack on May 02, 2016, 04:43:07 PM
Yep, 94-98. Midyear 98 they swapped to an oss which uses 32000ppm.
Google speedo calibrator. For $80+ id deal with the 4mph difference.
Google speedo calibrator. For $80+ id deal with the 4mph difference.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: Aerocoupe on May 02, 2016, 04:55:41 PM
Post by: Aerocoupe on May 02, 2016, 04:55:41 PM
I completely missed the part about no speedo cable in the OP's first post. Sounds like the OP has a definite and reasonably priced solution now. Great job guys!!
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: thunderjet302 on May 02, 2016, 07:23:40 PM
Post by: thunderjet302 on May 02, 2016, 07:23:40 PM
Quote from: JeremyB;455119
I think either the Speed-Cal (http://"https://www.dallasmustang.com/speed-cal-1994-2004-5-speed-cars.html")or Ford Racing speed-dial (http://"https://lmr.com/item/M4209ADPTAC/94-10-Mustang-Speed-Dial-Speedometer-Adjuster-M-4209ADPT-AC") will convert your 8407 pulses/min to the expected 8000 pulses/min. They run ~$100-130.
They specify 1994+ Mustangs because 1993 and previous Mustangs had mechanical cables.
I was going to say the same thing. It should fix his issue.
I've been thinking about getting one to correct the error in my speedometer (1% so at an indicated 70mph the car is actually going 69.3mph) and get rid of the 23 tooth gear so I can run a 21 tooth or lower gear. The thing is I can live with a less than 1mph error when the fix costs over $100.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: Haystack on May 02, 2016, 11:31:53 PM
Post by: Haystack on May 02, 2016, 11:31:53 PM
I lived with a 400% error in speedo for two years in my tbird. 1st gear was over 85mph.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: AT8 Cat on May 11, 2016, 11:16:41 PM
Post by: AT8 Cat on May 11, 2016, 11:16:41 PM
Wow, sounds like I've got a few options! You guys are awesome. Thanks for the good information, I'll have to sort through it all and figure out what's best for me. 7 kph isn't too bad, at least I'm going slower than what speedo says. I like the idea of swapping over to a t5 but that's probably a few years down the road. I appreciate the tips!
Cheers!
Cheers!
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: TheFoeYouKnow on May 17, 2016, 07:41:50 PM
Post by: TheFoeYouKnow on May 17, 2016, 07:41:50 PM
According to Late Model Restoration, your AOD speedo drive gear is 7 tooth. Mine is 7 tooth. Just scored a free 3.73 gearset today, so tomorrow I'm ordering a 20 tooth driven gear from LMR.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: thunderjet302 on May 18, 2016, 03:00:56 PM
Post by: thunderjet302 on May 18, 2016, 03:00:56 PM
Quote from: TheFoeYouKnow;455358
According to Late Model Restoration, your AOD speedo drive gear is 7 tooth. Mine is 7 tooth. Just scored a free 3.73 gearset today, so tomorrow I'm ordering a 20 tooth driven gear from LMR.
That applies to Mustangs. For some reason the Thunderbirds/Cougars got the 8 tooth drive gear in the AOD. Was your AOD originally from a Mustang? The factory AOD (which is still in my Thunderbird, just rebuilt) has an 8 tooth drive gear.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: TheFoeYouKnow on May 18, 2016, 03:06:53 PM
Post by: TheFoeYouKnow on May 18, 2016, 03:06:53 PM
Mine is originally from an 87 Mark VII. Add far as I'm aware from the research I did before my wide ratio mod, all AOD are 7 tooth until AODE and 4R70W. I had to retain my original output shaft for this reason.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: thunderjet302 on May 19, 2016, 03:18:13 PM
Post by: thunderjet302 on May 19, 2016, 03:18:13 PM
Quote from: TheFoeYouKnow;455365
Mine is originally from an 87 Mark VII. Add far as I'm aware from the research I did before my wide ratio mod, all AOD are 7 tooth until AODE and 4R70W. I had to retain my original output shaft for this reason.
HO AODs had the 7 tooth drive gear up till 89. After 1990 they have an 8 tooth drive gear (in Mustang applications). The standard output AODs (behind Thunderbirds, Cougars, Crown Victorias, Grand Marquis, and Town Cars) have an 8 tooth drive gear. I have no idea why Ford did this.
Title: How to correct speedo after changing to 3.73 on '88 Cougar
Post by: TheFoeYouKnow on May 19, 2016, 06:12:14 PM
Post by: TheFoeYouKnow on May 19, 2016, 06:12:14 PM
That could explain it.