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Old 04-11-2010, 12:02 PM   #1
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Default LS1 T56 with LT1 Adapterplate/InputShaft on LT1 Trans Am

Ok folks I've got a few questions about using an LT1 adapter plate and Input Shaft with an LS1 T56 on a '97 Trans Am.

Here's what's been goin on first:

In summer of '08 I had the ******** at Six Speeds Inc rebuild my transmission.

I've had issues all last summer and the summer before that with new clutches starting to slip within 1000miles of installing them (basically since Six Speeds Inc touched my transmission). Three clutches to be exact: two Spec2 Kevlars and one Spec1 Organic, and all 3 I babied for about 800 miles for break-in.

The last disk went to back Spec and they told me the disk was contaminated with some sort of oil and to check for a rear main seal leak, intake manifold oil leak yadda yadda yadda which I don't have (plus if there were motor oil leaks, they'd just get winged off the end of the flywheel and never touch the clutch anyways!). I pulled the transmission out last week to finally find the cause: red transmission fluid all over my input shaft.

Soooo I brought the transmission to a reputable transmission shop to have them check the front out, since it was most likely an input shaft seal leak-- which is exactly what it ended up being, they told me the input shaft seal was toast.

Next they ordered a new input shaft seal through either BorgWarner or Tremec (can't remember) using the part number on the transmission since GM doesn't carry the seals anymore. A new seal shows up the next day they doesn't look anything like the leaky seal that's on the tranny now. After some phone calls and research with Tremec/BorgWarner they determine that my transmission is actually an LS1 transmission with an LT1 adapter plate and input shaft.

Now this doesn't entirely surprise me because my car used to be automatic and I discovered a long time ago that the previous owner swapped in the T56. I'm guessing LS1 T56's are easier to a hold of than LT1 T56's so the previous owner did that and then slapped on an LT1 adapter plate and input shaft to make it compatible.

Here's the part that surprised me-- the rep from Tremec/BorgWarner told the shop that you're not supposed to use an LT1 adapter plate and input shaft on an LS1 T56 and that they should not give me any warranty if they do it. He didn't, however; come right out and say that it would not work (although I do know it did work for about 2 years before I had my transmission rebuilt). I've read a lot of threads on this website over the past few years and I could have sworn there were a bunch of guys that have done this swap successfully even though you're 'not supposed to' piece the tranny together like that.

So the main question I'm asking is-- Is there anything wrong with using an LS1 T56 on an LT1 car by using an LT1 adapter plate and input shaft????

The other part that surprised me is that the shop said that the LT1 T56's input shaft seal is integrated directly in with the adapter plate so in order to replace the seal you have to replace the entire adapter plate. So the second question I have is- is this true or can you just buy a new seal by itself?
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380whp & 382ft-lbs / 12.4 @ 116. needs traction.
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Old 04-11-2010, 01:58 PM   #2
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Your story's not sinking in 100%.. It sounds like you're getting alot of BS from the shop, but I don't want to call BS until I know for sure what you're calling an adapter plate.. Can you take and post pics? It would save alot of typing and guessing..
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Old 04-11-2010, 06:54 PM   #3
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I'd take some pictures but the transmissions at the shop right now unfortunately.

My vocab might be a little off since I don't know a whole lot about transmisions but I was pretty sure the 'adapter plate' was the front part of the transmission that houses the input shaft and allows the T56 transmission to bolt up to a particular bellhousing.

My T56, before it was in my car must have had an adapter plate on it to make it fit an LS1 f-body, and the previous owner unbolted it from the transmission and swapped it with an LT1 adapter plate and inputshaft to make it compatible with an LT1 f-body bellhousing and clutch. As to exactly what year and 'make' LS1 f-body it came out of, I have no idea. For obvious reasons the previous owner never bothered to share with me that the car used to be an automatic and that a T56 was swapped in, let alone that it was an LS1 T56.

As for the shop BSin' me-- I wouldn't be surprised about some of it. Like the fact that they're telling me they can't replace an LT1 T56 inpt shaft seal without replacing the entire front 'adapter' plate. That just seems like bullshit, I always thought the seal could be replaced by itself like any other transmission. But who knows.. I might have misunderstood them friday, and I'll ask again about it when I get in touch with them tomorrow (monday).

That's the best I've got right now, any help or answers to my questions would be greatly appreciated guys.
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380whp & 382ft-lbs / 12.4 @ 116. needs traction.
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Old 04-11-2010, 07:52 PM   #4
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The front case plate of the T56 is (ironically) called the mid-plate. It's where the LT1 clutch fork pivot mounts to and the LS1 hyd TOB bolts to.

As for the seal, the Input shaft seal is exactly the same between the LT1 and LS1 Fbody versions. The metal LT1 TOB tube sleeve has a rubber seal between it, but I've never had to replace the sleeve or a tube.

People swap between the LS1 and LT1 Input shaft and mid-plates all the time. With the exception of possibly needing to reshim the shafts, it's a very simple swap.
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Old 04-12-2010, 07:28 PM   #5
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Ok I got in touch with the shop and it turns out there were some miscommunications last Friday, although I didn't hear anything good this time around either.

Turns out that not only was the input shaft seal damaged, but the TO collar that is pressed into the midplate was also damaged even though it looked fine from the outside. The inputshaft seals between LS1 and LT1's are the exact same thing as you said also.

The part that sucks is that the TO collar/sleeve is pressed into the midplate-- which means I have to replace that along with the new midplate that comes with it. I'm gonna be waiting for a call tomorrow to find out exactly how much a new midplates gonna cost me (and frankly I've got a feeling its gonna be a ripoff).

The part that reeeally sucks is that since Tremec told the shop that they shouldn't warranty this job because you're "not supposed to" put an LT1 midplate on an LS1 T56, the shop won't do it for me. They said they'll get the new input shaft seal and midplate for me but won't install them.

That just blows because the whole damn point of me dropping my transmission off at a transmission shop was so that I wouldn't have to work on the transmission in the first place.
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1997 Trans Am M6 black
Lunati Voodoo 231/239 cam.. with stock heads, TPiS 58mm tb, Hooker lt's, Patriot Golds, Pro-Mag 1.6RR's, 4.10 Strange's etc..
380whp & 382ft-lbs / 12.4 @ 116. needs traction.
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Old 04-12-2010, 07:43 PM   #6
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Quote:
Originally Posted by tbag_skywalker View Post
Ok I got in touch with the shop and it turns out there were some miscommunications last Friday, although I didn't hear anything good this time around either.

Turns out that not only was the input shaft seal damaged, but the TO collar that is pressed into the midplate was also damaged even though it looked fine from the outside. The inputshaft seals between LS1 and LT1's are the exact same thing as you said also.

The part that sucks is that the TO collar/sleeve is pressed into the midplate-- which means I have to replace that along with the new midplate that comes with it. I'm gonna be waiting for a call tomorrow to find out exactly how much a new midplates gonna cost me (and frankly I've got a feeling its gonna be a ripoff).

The part that reeeally sucks is that since Tremec told the shop that they shouldn't warranty this job because you're "not supposed to" put an LT1 midplate on an LS1 T56, the shop won't do it for me. They said they'll get the new input shaft seal and midplate for me but won't install them.

That just blows because the whole damn point of me dropping my transmission off at a transmission shop was so that I wouldn't have to work on the transmission in the first place.
Still some questionable advice going on. You can buy a new TO tube (D&D sells them for $49: http://www.ddperformance.com/shop/pr...th=110_103_121

Easy enough to press the old one out and the new one in.

Sounds like you need to look for another shop..
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Old 04-12-2010, 07:58 PM   #7
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Quote:
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Sounds like you need to look for another shop..
I agree. My Six Speeds Inc LT1 tranny came with a LT1 mid-plate, Tremec main case, and Borg-Warner tailshaft. So SSI just mismatches the cases sometimes, but the internals are all the same (except for the input shaft). It shouldn't really make a difference.
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Old 04-12-2010, 10:55 PM   #8
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Great information guys, very much appreciated.

The only thing I don't completely understand what the TO collar could have to do with the input shaft seal going bad?

Is it just a coincidence that they both need to be replaced at the same time, or did one cause the other to fail??

I'm gonna get the transmission back tomorrow afternoon and most likely take the midplate off and have a look at whats goin on in there. I'm sure the shops gonna tell me something like $300 for a new midplate which then I'll tell them to politely **** off.

85MikeTPI-- how easy is it to remove the old TO collar and install a new one? Just wondering what's involved in it since I'm gonna be doing it myself.
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Lunati Voodoo 231/239 cam.. with stock heads, TPiS 58mm tb, Hooker lt's, Patriot Golds, Pro-Mag 1.6RR's, 4.10 Strange's etc..
380whp & 382ft-lbs / 12.4 @ 116. needs traction.
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Old 04-13-2010, 07:25 AM   #9
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Quote:
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Is it just a coincidence that they both need to be replaced at the same time, or did one cause the other to fail??

85MikeTPI-- how easy is it to remove the old TO collar and install a new one? Just wondering what's involved in it since I'm gonna be doing it myself.
The TO tube would fail if the trans was dropped, but otherwise I can't imagine.

It's simple enough to press out. Pressing the new tube in is just as simple and just needs a correct size drift to match the seal area of the tube.
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Old 04-14-2010, 08:40 PM   #10
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Alright I got my unrepaired transmission back today and here's what I've found.

1- After unbolting the midplate, the input shaft seal isnt ripped but it does look pinched a bit, so replacing it would more than likely fix my fluid leak problem. The input shaft looked nice and smooth around where the seal was seated.

2- Inspecting my TO collar, it looks completely fine, no wear and tear, nicks, scrapes at all. Which tells me that the shop was completely full of ****. Ohh yea that reminds me-- the shop told me they wont press in a new collar for me because of 'potentially damaging the aluminum midplate'. All they said they'd do was get me a new midplate with collar for $310 lol, and I promptly told them no thanks. As to what the TO collar could have to do with a leaky input shaft seal is beyond me anyways, (now that I've opened and looked at the inside of the transmission myself). I think they just wanted to make a few easy bucks.

3- There's a bearing race that seems to be pressed into the midplate which is preventing me from getting the old seal out and I was under the impression that the race and shim would fall out when I unbolt the midplate off the transmission. Is this normal?

4- Before I unbolted the midplate, before I even brought the transmission to the shop, I noticed there was a very small amount of play in the input shaft, and I've also heard that is NOT good. When I asked the shop, they told me the opposite-- that the shaft spins on conical bearings which are supposed to do that. Now I'm no mechanic but I was under the impression that conical bearing are supposed to be preloaded enough so there isn't any play-- like for a pinion gear in a differential. Could this mean that the race that seems to be pressed into my midplate just need to be shimmed out more?

Any input would be greatly appreciated.

As long as the little bit of input shaft 'play' is normal, I feel pretty comfortable enough to replace the pinion seal myself. If not than I think its time to bring the trans to a shop that doesn't suck.
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Lunati Voodoo 231/239 cam.. with stock heads, TPiS 58mm tb, Hooker lt's, Patriot Golds, Pro-Mag 1.6RR's, 4.10 Strange's etc..
380whp & 382ft-lbs / 12.4 @ 116. needs traction.
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Old 04-15-2010, 07:30 AM   #11
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3- There's a bearing race that seems to be pressed into the midplate which is preventing me from getting the old seal out and I was under the impression that the race and shim would fall out when I unbolt the midplate off the transmission. Is this normal?
The races in the mid-plate are slip-fit. If going in or coming out perfectly straight, they'll slip out. Otherwise, they can appear to be pressed in, but in fact they should spin easily when fully installed. Sometimes the trick is the drop the mid-plate onto a soft piece of wood, and the races/shims will fall out.

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4- Before I unbolted the midplate, before I even brought the transmission to the shop, I noticed there was a very small amount of play in the input shaft, and I've also heard that is NOT good. When I asked the shop, they told me the opposite-- that the shaft spins on conical bearings which are supposed to do that. Now I'm no mechanic but I was under the impression that conical bearing are supposed to be preloaded enough so there isn't any play-- like for a pinion gear in a differential. Could this mean that the race that seems to be pressed into my midplate just need to be shimmed out more?
The factory shim specs (end-play) results in the input shaft having some play at the pilot. Even with 0.000-0.002 preload, the input can have slight play at the pilot. Over 0.002 bearing shim preload will usually keep the input shaft from moving, but can lead to premature bearing wear..

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Old 04-16-2010, 01:53 AM   #12
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I did some homework with a dial indicator tonight:

The end play at the tip of the input shaft was .001" which was just as it should be.

I also was told there shouldn't be any side-to-side play.... in my case I had roughly .035" of side play at the tip of the input shift. Oh and my pilot bearing was toast when I took the clutch out, too, which probably had something to do with it.

That can't be a good thing. If its something I can't fix myself, looks like I'm gonna have to try to find a good transmission shop around here again, tell them my situation and hope they can fix it.
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380whp & 382ft-lbs / 12.4 @ 116. needs traction.
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Old 04-16-2010, 07:36 AM   #13
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Since you have input shaft shim end-play, you'll have movement at the pilot. If you want to reduce the movement, you'll need to add pre-load to the input shaft shim as mentioned above.
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Old 04-16-2010, 10:53 AM   #14
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Since you have input shaft shim end-play, you'll have movement at the pilot. If you want to reduce the movement, you'll need to add pre-load to the input shaft shim as mentioned above.
I don't think I'm completely understanding you-- I thought .001" end play (forwards back wards movement) was perfectly normal at the tip of the input shaft.

Shouldn't I be looking for a way to eliminate the side-to-side play at the tip instead?

Also, if I do need to add bigger shim to the input shaft, it would go between the midplate and bearing race that's slip-fitted into the midplate right?

I've got a dial indicator, dial caliper, black rtv, and a torque wrench so I think I've got all I need to do this job except the shim(s).
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Old 04-16-2010, 11:50 AM   #15
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I don't think I'm completely understanding you-- I thought .001" end play (forwards back wards movement) was perfectly normal at the tip of the input shaft.

Shouldn't I be looking for a way to eliminate the side-to-side play at the tip instead?

Also, if I do need to add bigger shim to the input shaft, it would go between the midplate and bearing race that's slip-fitted into the midplate right?

I've got a dial indicator, dial caliper, black rtv, and a torque wrench so I think I've got all I need to do this job except the shim(s).
The "factory" spec is for input shaft end-play, from which you will have input shaft "wiggle" at the tip. If you want to eliminate the wiggle, you have to pre-load the input shaft with more shim than measured. The shims go into the midplate, under the bearing races.
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Old 04-16-2010, 12:28 PM   #16
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I think they just wanted to make a few easy bucks.

4- Before I unbolted the midplate, before I even brought the transmission to the shop, I noticed there was a very small amount of play in the input shaft, and I've also heard that is NOT good.

Shouldn't I be looking for a way to eliminate the side-to-side play at the tip instead?
Aren't you glad you opened it up yourself?

The T56 has a tighter input shaft end play than other older trans. that had loose rollers. The pilot bearing is how you will eliminate the side-to-side at the tip. As you toasted your last roller(?) pilot, bronze is a very valid option.

Personally, I wouldn't mess with the end play at those numbers.
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Old 04-16-2010, 12:28 PM
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