Using an automatic from a 2.5 on a 2.8 engine (Page 2/2)
handymanpat OCT 27, 10:12 AM
Ok, I am going for it!
I think for the occasional driving and easy driving she does it will be good to go.
At least we can get her car back on the road!
Thanks Pat

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pat moody

[This message has been edited by handymanpat (edited 10-27-2022).]

olejoedad OCT 27, 10:57 AM
In 1986, the TH125C had a final drive of 3.06 with the 2.8 V6, and a final drive ratio of 3.18 with the 2.5 L4.

The car might seem peppier with the 2.5 transmission and the V6.
Raydar OCT 28, 07:15 PM
I just saw this, but I'm happy that you are proceeding.

As posted, previously, the gear ratios are likely different, but that's not a show stopper. Speedo info is grabbed from the axle speed, so it will be accurate.
The shift points may be a bit "early", but that shouldn't be a show stopper, either. (And will help MPG.) If this is a problem, a careful (mis)adjustment of the TV cable may change things a bit. Maybe.

Having said all of that... Ed Parks made the statement, once, that the V6 transaxle had an extra pair of clutch disks, over the 4 cylinder version.
Even if that's true, I suspect it won't make much of a difference, unless your wife has a heavy foot.

I think I would be inclined to use the V6 torque converter.
The Duke converter is probably designed to maximize torque transfer. (i.e., "looser) so the V6 may rev a bit more for the same "forward motion".
All speculation, however. No idea where to look it up, either. If I find something, I'll jump back in.

As others have said, the TCC should be happy, if it works now.
handymanpat OCT 28, 10:53 PM
Yes, she has been without the car for a long time, at least a year.
We spent a lot of time and trouble on that sparkle car and were so disappointed in the work that was done, especially since we considered the guy to be a friend and fellow fiero enthusiast.
I could understand him not wanting to take the engine back apart to locate and fix his mistake but he was unwilling to even acknowledge there was a problem!
We pulled the engine and were going to put a 3800 in it but she did not want an engine like that in her car.
So I'm putting the 3800 in my black car and using my stock v6 for her car.
Someday this will all get done, I spend my weekends and many evenings working on my "fleet"
Thank you to all you guys and for all the help.
I expect to have e a couple cars up and running and in the events and things for next year.
We will see all you guys at the 40th!
Watch for that pink car, you will know we are around there somewhere!
Thanks Pat

QUOTE]Originally posted by Raydar:

I just saw this, but I'm happy that you are proceeding.

As posted, previously, the gear ratios are likely different, but that's not a show stopper. Speedo info is grabbed from the axle speed, so it will be accurate.
The shift points may be a bit "early", but that shouldn't be a show stopper, either. (And will help MPG.) If this is a problem, a careful (mis)adjustment of the TV cable may change things a bit. Maybe.

Having said all of that... Ed Parks made the statement, once, that the V6 transaxle had an extra pair of clutch disks, over the 4 cylinder version.
Even if that's true, I suspect it won't make much of a difference, unless your wife has a heavy foot.

I think I would be inclined to use the V6 torque converter.
The Duke converter is probably designed to maximize torque transfer. (i.e., "looser) so the V6 may rev a bit more for the same "forward motion".
All speculation, however. No idea where to look it up, either. If I find something, I'll jump back in.

As others have said, the TCC should be happy, if it works now.[/QUOTE]

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pat moody

OldsFiero OCT 29, 10:46 AM
The extra clutch is worth about 20% in torque capacity. Not going to look it up, but if I recall from the 90's when I was rebuilding at least 1 a week, the 2.5 and the 2.8 had the same clutching. The smaller engine J cars had 1 less.
My father had an 84 Cutlass Ciera with the duke. It was slug on the hills here. When the trans failed and I tore it down, it had a 2.84 final. It had a 37 tooth drive sprocket and 33 driven. I swapped in a 33 drive and 37 driven from a J car. What a difference going from over driven sprockets to under driven made! He said he gained a couple MPG in this terrain as well.

Git er' done!

Marc
Raydar OCT 31, 04:54 PM

quote
Originally posted by OldsFiero:

The extra clutch is worth about 20% in torque capacity. Not going to look it up, but if I recall from the 90's when I was rebuilding at least 1 a week, the 2.5 and the 2.8 had the same clutching.
...



Thanks for that. The Fiero trannies were so similar that it really doesn't make sense for there to be such a difference.