4T60E interchangeability

[Jrs3800]

Yes... This is what we have been trying to tell you... Its easier to get an F79 2.97 Ratio trans from a supercharged car as opposed to trying to make what you have work..

[spoiledred94]

Well I thought I wanted to change the ratio. I guess this it then. I'll be looking to install the new trans the week after next.
I got a hoist off of craigslist. $50 and the seller helped me disassemble it and put it in my car.

[Jrs3800]

Make sure the trans you get is 1994 or 1995.... 91-93 will not work for you..

[willwren]

150 for endplay adjustment? Borrow or rent a dial indicator and do it yourself. The thrust washers for endplay adjustment are NOT expensive. However, it requires assembly-check-disassembly-change washer-assemble.

I personally feel you're way in over your head simply for the fact that you've never messed with a fwd trans. You don't want this to be your first crack at it. You need someone that knows what they're doing to be in there with you.

No, your final drive with the HD diff won't be 3.33, it'll be 2.97, as the drive/driven sprockets combined with the 3.33 diff result in a 2.97:1 ratio. Your shift points will be fooked and you'll get crappy mileage.

I stronly suggest you get a non-HD trans and simply do a dircect swap.

[willwren]

Spoiledred94 is directly North of me in WA.

Determination is only half the battle. The logical path here needs to be followed. I suggest the non-HD trans for now, and when the L67 swap is ready to happen, he obtains the whole drivetrain and subframe intact, including the wiring harness and PCM. That way he also gets the HD drive axles, proper ratio, and the FE2 front end components as well.

[Jrs3800]

That I can agree with...

[alec_b]

I'll ask this here, so as to keep the threads down and stay on topic. I've also gotten to thinking about ratios, and why the supercharged cars all got stuck with a 2.97 ratio. I just finished replacing the trans. on a '96 SE, with the 3.06 ratio. I test drove it today, and to be honest other than at full throttle is felt just as powerful as my '96 SSEi. The main difference I noticed was that the SE did 2k @ 60 MPH, where as my SSEi does 15-1600 @ 60.

If I already have the HD trans, which I do, what's the easiest way to shorten up that 2.97 ratio a bit. From reading this, it seems just as hard as putting an HD trans in a non-hd car. Or am I way off?

[gonzo4191]

it got the 2,97 to best mix fuel economy of granny gears and the 3.06 fun ratio in sle's and some se's

[Jrs3800]

I'll ask this here, so as to keep the threads down and stay on topic. I've also gotten to thinking about ratios, and why the supercharged cars all got stuck with a 2.97 ratio. I just finished replacing the trans. on a '96 SE, with the 3.06 ratio. I test drove it today, and to be honest other than at full throttle is felt just as powerful as my '96 SSEi. The main difference I noticed was that the SE did 2k @ 60 MPH, where as my SSEi does 15-1600 @ 60.

If I already have the HD trans, which I do, what's the easiest way to shorten up that 2.97 ratio a bit. From reading this, it seems just as hard as putting an HD trans in a non-hd car. Or am I way off?

There are reasons for this...

the 3.06 was more of a 3800 performance minded gear ratio.. It runs more along the lines of 1700-1800 @ 60... Some of the clusters are off by as much as 200-300 Rpms...

The L36/L26 were all 9.4 : 1 compression where the SC cars were all 8.5 : 1 compression as they were boosted... The 3.06 does give the L36 a more sporty and strong feel..

The L67 uses the 2.97-2.93 as it has gobs of torque all around.. also helps keep fuel economy numbers up.. While under boost you could be running 10-11 : 1 compression IIRC..


I have a 2.97 ratio in the van... we could call this an HD trans as it has all of the parts.. This trans is( well was ) being twisted by a Series I 3800 L27 Tuned port... with 1.8 rockers among a few other mods.. Impression from people who drove it were pretty good.. And it did a mixed mileage of 24 Mpg consistently... But being that van that it was it really needed a 3.06 to get it around easier... with the 2.97 the van did feel a bit heavier but very driveable..

when we start talking interchange things really start to get a little hairy.. I am learning bit by bit as I dork around with the 4T60E's, and there were changes between years and they also differed for various models..

Our cars used 2.84-2.86, 2.93-2.97( 3.29 & 3.33 Diffs Overdriven ), 3.05-3.06

Other years could be had with 87-88 could be had with 2.73( 2.73 is a 3.06 Diff thats Overdriven ), 87-91 could be had with 2.84 or 2.97( 3.33 Diff overdriven ), 89-91 could be had with 3.33...

[alec_b]

It seems to me that the 3.33 would be really fun, but not so great for the MPG's.

That's the major reason I love this thing over my STS. 3.71 gears in that thing, it was really winding out. 2.97's in the bonne, and at 45 in lockup I'm loping around at 12-1300 rpm's. It's great.

[Jrs3800]

3.33 does hurt the mileage... But for me I am going back to the 35/35 gear set... This will give me the ability to get a 3.06 diff and swap it in if the 3.33 seems like overkill by any means.. Not sure yet.. Its almost giving myself an easy out if that makes any sense.. 3.06 is the heaviest ratio I will use in the van..

after doing the 2.97 I will most likely never use that ratio again, unless its in the 91 LE bonneville...lol

[willwren]

FYI, the 3.33 was last available in the NA L27 91 SSE. IIRC, jr's3800 has the 3.33 in his 90 SSE (not the 90 LE, or either of his other two Mr. 4 3800 bitch that he is).

To get the 3.33, you have to use the 3.33 HD (supercharged if you will) diff, with a drive/driven ratio of 1:1 in your trans.

[alec_b]

Oh I see, so in theory it could be done? If I'm understanding correctly, use the FD that's in my HD right now, but switch the drive/driven gears for ones out of a 3.33 90-91 SSE? Hmm...

Well, maybe if this tranny dies I might consider is. This ones got warranty until september, so I'm hoping it goes down before then and I can get another one

[Jrs3800]

3.33 would be almost insane with the SC 3800... But it may be fun as well.. Being that you have a 96 you will have a 3.29 ratio if you went with the 35 Drive and 35 Driven gears..

The 2.84 and 3.06 both use the 35/35 gear set

The 2.97 uses the 37 / 33 gearset which overdrives the 3.33 diff for an overall 2.97 or in your case a 2.93... So yes if you went to a 35/35 gear set you would have a 3.29 ratio as your diff will be driven like Bill stated at 1:1 meaning you have a 3.29 diff that simply overdriven to be a 2.93

[spoiledred94]

Well howdy cowboys! Actually the info above sealed up the last of my confusion as far as the ratios and how to determine them are concerned.


if you divide the drive number by the driven number you get a quotient . If you divide the diff ratio by the above quotient you get the FDR

In my case with the HD diff(3.33) and 37/33 drive and driven:

37/33 = 1.12
3.33 / 1.12 = 2.97 FDR


With my non HD trans I have a 2.84 diff and a 35/35 drive and driven:

35/35 = 1.00

2.84/ 1.00 = 2.84 FDR

If I put the non HD diff (2.84) on the HD trans (37/33 drive and driven)
I get:

37/33 = 1.12

2.84 / 1.12 = 2.53 :(

All of this was posted way earlier and I didn't get it until last night.

So my best choice if I can't get a 3.06 diff from a 94 or compatible would be to leave the differential on the HD and go with 2.97 FDR. I can't imagine I'd be happy with that. I am pretty close to out of project money, but can you give me range of cars that would have the 3.06 diff? If I could order from A GMC dealer it would prolly be 1700 dollars or something!! And I don't think I want to go pull one out of a junkyard. If I did go the junkyard route can I pull the diff w/o pulling the trans? Is it likely that I could find one already pulled or would they only be selling the whole trans.

At any rate could you do me that favor an tell me wich cars and years and trim level would have my 3.06 diff.
Kris

[bonnevillain]

Anything non-supercharged has a chance of having it i believe. Easiest way to find out would be to check the RPO codes in the trunk (assuming you are going to a junkyard)

[spoiledred94]

Thank you my friend. I think there is a list RPO codes somewhere here a Pontiac Bonneville Club.com


"Edit: I found the 3.06 RPO code. It's FW2"

[alec_b]

If you need a FW2 diff, I have one from a junk tranny I just pulled out. The 3rd gear was out but otherwise it's in fine shape. If you'd like the 3.06 diff I'd be happy to pull it for you and box it up after work some night. PM me if you're interested.

It's from a '96, BTW.

[Jrs3800]

A 96 3.06 will not work for him... Different gear pitch

Needs to be 91-95 3.06

[alec_b]

That's too bad...

Guess I'll just toss it with the trans then.