Author Topic: Which Transmission do you think is the best way to go? (Read 2897 times)

Noodlewad · « **on:** December 06, 2004, 09:25:02 am »

Hi all, hope I can get some responses to help me out with my conversion.
I'm putting a TD into my 81 Cabrio. I have a few transmissions to choose from at the moment.

Code ----- Final --- 1st ---- 2nd ---- 3rd ---- 4th ---- 5th
(FN) ------ 3.89 --- 3.45 --- 1.94 --- 1.29 --- 0.91 --- 0.71
(7A) ------ 3.94 --- 3.45 --- 1.94 --- 1.29 --- 0.91 --- 0.71
(ACH) ----- 3.94 --- 3.45 --- 1.94 --- 1.37 --- 1.03 --- 0.89

Currently the Cabrio has the FN in it, shifting/well.
The 7A is acutally attached to the TD motor
I don't think I want to go with the ACH, but I do have it available.

There isn't too much of a difference in speed between the FN and 7A, about .7mph at 2500rpm.
I don't think that 3.89 vs 3.94 final will have much of an affect on acceleration. Is this correct?
Keep in mind that I do about 50miles round trip a few times a week to get to a worksite.

So what is your opinion on the easier swap?
Would it be easier to just pull the gas motor from the Cabrio and put in the TD off the 7A?
Or would it be easier to pull the entire motor/tranny from the Cabrio and put the entire 7A/TD assembly into the car?
I've done engine/tranny swaps on my CJ-7 a few times, but havne't done a FWD car before.

Nate

VWRacer · « **Reply #1 on:** December 06, 2004, 11:20:31 am »

In the end the answer depends on your goals. If it is the fuel economy as your post implies, then sticking the 7A/TD combo in is that most straight forward option, assuming the axles fit. There is virtually no difference between the fuel economy of the FN vs the 7A - after all, how much time do you spend in first gear?

And don't worry about 1st gear acceleration, you wind through this gear so fast anyway with a diesel that you will never notice the difference.

But while you have the TD on the floor, I'd put a new clutch in it!

jtanguay · « **Reply #2 on:** December 06, 2004, 12:38:57 pm »

ya i agree, put in a good clutch if it's already out.

you'll see good fuel economy with a brand new clutch!

jon

Greasemonkey · « **Reply #3 on:** December 09, 2004, 07:06:12 am »

Quote from: "Noodlewad"

Hi all, hope I can get some responses to help me out with my conversion.
I'm putting a TD into my 81 Cabrio. I have a few transmissions to choose from at the moment.

Code ----- Final --- 1st ---- 2nd ---- 3rd ---- 4th ---- 5th
(FN) ------ 3.89 --- 3.45 --- 1.94 --- 1.29 --- 0.91 --- 0.71
(7A) ------ 3.94 --- 3.45 --- 1.94 --- 1.29 --- 0.91 --- 0.71
(ACH) ----- 3.94 --- 3.45 --- 1.94 --- 1.37 --- 1.03 --- 0.89

5th gear on the ACH is actually a 0.75, and it is a proper diesel tranny. I'd run that, plus it's probably the newest of all 3, more likely to last longer. Don't forget to change the oil and all seals while you have it out.

Peter · « **Reply #4 on:** December 09, 2004, 08:45:30 am »

I have both trannys(FA&ACH)...ACH would be my choice,well rounded tranny for diesel application in the city and on the highway without to much reving....75 is the correct #

Dr. Diesel · « **Reply #5 on:** December 09, 2004, 09:07:51 am »

go with as long a ratio as possible. don't forget to make sure you inner CV joints match the size of the tranny's output flanges!

Greasemonkey · « **Reply #6 on:** December 09, 2004, 09:41:38 am »

Hey, while we're on the topic of trannies, I do my own tranny work and I will be rebuilding a tranny to go with the rebuilt diesel I'm (slowly) working on. I have everything I need to regear an ACH to this:

1st 3.45
2nd 2.12
3rd 1.44
4th 1.03
5th 0.75
FD 3.67

The engine will be a 1.6TD modified to somewhere around 90-100 HP (I hope). Does anybody see anything wrong with the combos? The rev drops are nice and even, getting progresively closer toward 5th, with a tall gas-engine ring and pinion. I'm wondering if the 2.12/1.44 2nd/3rd are too close for a diesel and if I should keep the original ACH ratios and just put a 3.67 FD in it. Would the engine be able to easily pull with the taller gears?

Any thoughts?

TDIMeister · « **Reply #7 on:** December 09, 2004, 02:38:58 pm »

Why not CTN?

ricosuave · « **Reply #8 on:** December 09, 2004, 09:21:51 pm »

http://autos.groups.yahoo.com/group/Audi-VW-Diesels/message/17244

Peter · « **Reply #9 on:** December 10, 2004, 07:24:24 am »

I think you need to ask yourself... what type of driving you will be doing as to what is best...for example I like the ACH tranny because I can drive around town in 5th gear without lugging the engine and conserve on fuel...on my jetta of the same year which is a turbo, I can only drive in 4th gear...

Quote from: "Greasemonkey"

Hey, while we're on the topic of trannies, I do my own tranny work and I will be rebuilding a tranny to go with the rebuilt diesel I'm (slowly) working on. I have everything I need to regear an ACH to this:

1st 3.45
2nd 2.12
3rd 1.44
4th 1.03
5th 0.75
FD 3.67

The engine will be a 1.6TD modified to somewhere around 90-100 HP (I hope). Does anybody see anything wrong with the combos? The rev drops are nice and even, getting progresively closer toward 5th, with a tall gas-engine ring and pinion. I'm wondering if the 2.12/1.44 2nd/3rd are too close for a diesel and if I should keep the original ACH ratios and just put a 3.67 FD in it. Would the engine be able to easily pull with the taller gears?

Any thoughts?