No problem, on a T-400 the speedo cable attaches to the speedo gear holder and its easily removed. There are charts to specify what speedo gear you need for most gear ratios and tire sizes. For really low ratios an adapter is needed but you should be fine with 3:55's. I'm guessing you need a lime green (34 tooth) for 29" tires or orange (35 tooth) for 28" tires and 3:55's. T-400's have unique gears, larger than the others.
Thanks Randy
-- Edited by GLHS60 on Friday 13th of June 2014 05:51:14 PM
I have a number of the TH400 speedo gears. They're color coded by the number of teeth on them. Still available through GM, but it's a bit of a guessing game to get the right one. I needed to change by 2 or 3 teeth when I put the TH400 in the convertible, as it has 2.73 gears, compared to the 2.56's in my Parisienne that the motor/tranny came out of.
Thanks for the good info, It is a 28" tire on a 3.55.
As I'm to understand you can go 2 gears at a time up or down until you basically hit the one you need. I've heard guys just hook up a GPS and use that to calibrate.
So I should be good just changing the removable gear on the cable side. Shouldn't have to do the one on the output shaft?
Cheers, Mark
__________________
65 Laurentian post, 67 Grande Parisienne 4 door HT.
Any Idea what standard rear end ratio my 67 would have? 2.73, 3.08? What was the standard ratio for these cars with no performace options? Barring the 327/275, the car has none.
And beyond that, what colour drive gear would my TH400 likely have?
__________________
65 Laurentian post, 67 Grande Parisienne 4 door HT.
To calibrate mine I went on the highway and used the crossroads as mileposts. When they surveyed Western Canada back in the early 1900's they left a 66' road allowance between every mile east west, and every 2 miles north south. I get a nice straight stretch about 10 miles long and use that. As a teenager I worked on the survey crew of a siesmic company and learned about the road allowances. I just needed clarity if the 66' was part of the mile, or in addition to the mile. They're part of the mile.
