t-5 and speedo gear questions.....

[Michael Yount]

Sorry Jaided - don't know how I missed that. So, what's it reading, and what do you think it SHOULD be reading? Have you got someone with an accurate speedo that can time you? Whatever the % difference is, that's the % difference you need to make with a gear change.

Example. Let's say it's reading 60, but it should be reading 75. That means it's reading 25% too slow. If it has a 19 tooth in there now, then you need a 25% change in the driven gear which is like a 14 tooth. 16 is the lowest I've seen. So you can put a 16 in, and still be about 10% off; or you'll have to change the drive gear to the next highest one.

Have you checked to see what drive gear you have? If you know the % you're off, and what drive and driven gear you have, we can figure out what combo will get you there.

 

[joelliott]

In my 85gt, I have the stock tranny, t5 and stock gear rear end. Does anyone know what drive gear is in a 1985 T5 tranny? Thanks
Joe E.

 

[jaidedeye]

im not sure what gear is in the tranny but i did install a black 20 tooth gear on the speedo cable. dammit!!!! i just ordered bigger gears when i should have done smaller

i do have another question though. the tranny the car came out of had an 85mph speedo in it with the 20 tooth and 3.55 gears.

i have the 140 speedo, will that change anything?

i really think i am 15 mph off. for example when i drive around on base the speed limit is 35 mph well if im keeping pace with some one my speedo says 20 mph....ill have someone follow me or find someone who has a gps that can tell me exactly how fast im going...

 

[Michael Yount]

Joe - unless you know the complete history of the tranny, you're better off looking inside the speedo cable port and seeing what color it is - determining it that way. It could've been changed. However, according to the link I posted in my first post way up above, it's a 7 tooth OEM.

Jaided - Well, now we get Paul Harvey - page 2, the REST of the story. So you've changed tranny, rear gear and SPEEDO. And you're perplexed why all the standard remedies don't seem to be working? (Chuckle here....) Yup - get someone to pace you, or use mile markers and a stop watch on the Interstate so you can find out exactly what percentage your speedo is off. If you come back in here with that info, we can help you figure out what you need to do. I'd suggest you measure it at a lower speed and a higher speed - say 30 mph and 70 mph.

 

[jaidedeye]

at 35 mph my speedo is at 30 mph,

at 60 mph my speedo reads 51 mph...had a friend pace me

 

[Michael Yount]

....and, we need to know (for sure) how many teeth on your drive gear, and how many teeth on your driven gear. You'll have to pull the speedo cable out of the tranny to determine this. The color codes for the drive gear are further up the thread.

 

[jaidedeye]

ok ill check them too

 

[Michael Yount]

Good news though - looks like you're only off 10-12%; should be able to correct that by going about 2 teeth smaller on your driven gear. But let me know what they are, and we'll do the calcs in the thread.

 

[jaidedeye]

ok, thanks michael.