North American Turbocoupe Organization



Some transmission info - T5 swap
Sophosis Offline
Member
#1
So I'm getting ready to mate the new trans to the new motor before I drop them in as a pair. Time to decide if I want to monkey around with the 5th on the trans going in or not.

Here's some info:

1997 Mustang V6 T5
Input length: 7.85 inches
Pilot diameter: 0.668 inches
Input shaft: 23 teeth
"Bigger" input shaft bearing
Steel throw-out bearing tube on input retainer

1988 Turbocoupe 4cyl T5
Input length: 7.41 inches
Pilot diameter: 0.590 inches
Input shaft: 19 teeth
"Smaller" input shaft bearing
Aluminum throw-out bearing tube on input retainer

Input shaft length measures from the face of the transmission to the end of the shaft, so when it is installed.

To make this work, I had a machine shop cut down the V6 input shaft to 4cyl specs. Even though this will cut through the case hardening on the shaft, I don't think it will make much difference since the area makes contact with roller bearings. The guy that machined it seemed to agree and I found a few other cases around the internet that seemed to agree. If the pilot bearing goes bad, that might be another story. At least these input shafts are abundantly available. Looks like I'll find out first hand.

Fifth gear - I needed the following info to crunch some numbers:
4cyl T5:
Teeth Input/Countershaft: 19/33
Teeth Fifth/Countergear: 27/59
Ratio: 33/19 * 27/59 = 0.7948

V6 T5:
Teeth Input/Countershaft: 23/34
Teeth Fifth/Countergear: 25/51
Ratio: 34/23 * 25/51 = 0.7246

I could have swapped fifth gears, and this would've given me a ratio of 0.598... quite a low ratio/high gear. Using 3.55s and a 26.2 inch tire:

Ratio - RPM @ SPEED
0.598 - 2125 @ 77.8 (swapped)
0.725 - 2567 @ 77.8 (stock v6)
0.795 - 2815 @ 77.8 (stock 4cyl)

0.598 - 1640 @ 60
0.725 - 1980 @ 60
0.795 - 2173 @ 60

So, I think if I'm going to run 3.55s, which I am not changing for the near future, I should probably stick with the stock 5th gearing for the V6 trans.

Just for fun, running a 4.56 rear gear would put 60mph back at 2100 rpm.. so marginally better than stock. Final 1st ratio would be 15.276, compared to stock's final 1st of 14.094.

Oh, forgot to add, if nothing else, I needed to dive in to swap the speedo drive gear. Tbird's is 6 tooth and the Mustang's is eight tooth.


Attached Files Image(s)
   
1988 Turbo Coupe
- 0.020 Diamonds w/stock rods, T3 w/stock IC, BoPort 1.5 cam, LA3 w/QH on MAF, water/meth
- 5-lug swap, 31-spline, 4.10s, vacuum brakes, PBR front brakes, 2000 Mustang GT 17" rims
Reply

Bungy Offline
Member
#2
Looks like you did the exact same thing I did. I turned down a 95 trans input shaft, used a 6 tooth gear, and did the math every which way from Sunday. I decided to keep the .72 overdrive. If you get too low (numerically) you'll end up lugging the 4cyl in OD.
I've read on other forums a lot of guys running the turned down shafts and haven't heard of any problems with wear.
1986 TC 100% Stock

"Nitrous is for guys who can't build motors"

Reply

TurboCoupe50 Offline
Posting Freak
#3
Sophosis Wrote:Just for fun, running a 4.56 rear gear would put 60mph back at 2100 rpm.. so marginally better than stock. Final 1st ratio would be 15.276, compared to stock's final 1st of 14.094.

BUT the D/S RPM would be far higher than stock, would want a closely balanced shaft for running at highway speeds...
1988 Turbo Coupe331 AOD

1972 Comet GT

1969 Fairlane Cobra 428CJ 4-Speed
Reply

Sophosis Offline
Member
#4
Bungy, that's good to hear.. I've seen some similar posts about the turned down inputs. I checked the depth into the pilot bearing before I bolted everything up and everything check out, so time will tell.

TurboCoupe50, I didn't really think about that.. but yea I guess it would. Luckily, if I were to go that route, I'm already set. I had to buy a new driveshaft, aluminum from The Driveshaft Shop, not long ago.. old one was bent and the shop I first took it to more/less took my money for balancing it.. they say it checked out true .... it didn't. I was so happy with the new driveshaft.. that car had never driven that smooth as long as I had it.

I only lack about 3 hours work to get the car to where I can fire it. Even though I had the time today, it's outside without the driveshaft connected and it's 24F out currently.. didn't even break freezing today. One week ago, the day high was 60F *sigh*
1988 Turbo Coupe
- 0.020 Diamonds w/stock rods, T3 w/stock IC, BoPort 1.5 cam, LA3 w/QH on MAF, water/meth
- 5-lug swap, 31-spline, 4.10s, vacuum brakes, PBR front brakes, 2000 Mustang GT 17" rims
Reply

TurboCoupe50 Offline
Posting Freak
#5
Sophosis Wrote:Even though I had the time today, it's outside without the driveshaft connected and it's 24F out currently.. didn't even break freezing today. One week ago, the day high was 60F *sigh*

LOL, well if you're expecting sympathy from me you have a long wait, I'm in the same boat... Well at least my project is inside, but my garage is impossible to heat at below about 45*...
1988 Turbo Coupe331 AOD

1972 Comet GT

1969 Fairlane Cobra 428CJ 4-Speed
Reply





Users browsing this thread:
1 Guest(s)



Theme © iAndrew 2018 - Software MyBB