Speedometer Calibration on 87 Cutlass

[cutlass00]

I recently replaced the TH200 trans on my 87 Cutlass with a TH200-4R from a 1987 Monte Carlo SS. The 200 was giving me fits, so I figured it was time for a change. I have the new transmission installed, but now my speedometer is way out of whack. After talking to someone from a specialty transmission shop, they said my speedometer is reading 39% off! He recommended that I buy a $75.00 reducer that fits between the end of the speedometer cable and the transmission housing, and that this would fix my problem. Has anyone else done this sort of swap before and had the problem I am having?

 

[crucial118]

Never had to do that on my Cutlass, but when I ordered my TH350 for my 67 Lemans the guy asked what type of rear gearing I had and what size tires on my ride so that he could install the right gears for the speedo cable.

 

[cutlass00]

Never had to do that on my Cutlass, but when I ordered my TH350 for my 67 Lemans the guy asked what type of rear gearing I had and what size tires on my ride so that he could install the right gears for the speedo cable.

That's initially what I did, but apparently the trans I put in my car is SO much different than the old trans and rearend combination that simply changing the drive gear or driven gear will not work. Originally I changed the driven gear because the guy told me that I need to buy a 27-tooth gear and that would put me "within 5mph" of a true speedometer reading. This did make a 5 mph difference, but it still reads 15mph off at 60mph.

 

[crucial118]

Damn, that's way off. Sorry I can't help you on this, I've never made that swap before. Good Luck

 

[Mudweizer]

See if this site helps you: http://www.bgsoflex.com/speedo1.html

or this one: http://www.montess.org/speedo_gears.html

then check here to see if available: http://www.transmissioncenter.net/speed ... va.htm#200

Good luck! 🙂