Transmission / Overdrive: GM Transmission Adapter Kit Issues

[JoeHall]

I don't get on here much anymore, but currently working on a GM transmission swap, and ran into a couple of issues someone here may be able to help with.

I am installing a 700R in a GT Hawk, using a Stude vendor's adapter kit. First & foremost: The GM torque converter pilot snout is 1.703" OD, but the hole in the adapter, the snout fits into, is 1.780" ID. The pilot fit is what keeps the TC centered, and near as I can tell should be around .002" to .003". So .075" of slop just ain't gonna cut it.

I thought maybe I'd simply received a bad one. But after reading the archives here today, I found a thread posted in 2009 that mentioned the same problem, and another thread posted today that mentioned the same problem with a very recent install. Both of those threads concerned kits from another vendor.

So it seems different vendors, but maybe a common supply source. I suppose a machinist could make a sleeve, but cannot believe it is necessary. In the kit's instructions there is nothing alluding to this issue. I think maybe I am missing something here.
Has anyone else experienced this? If so, how did you deal with it?

Another issue: Beefy alignment dowel pins are in place to keep the transmission from ever shifting on the adapter plate. However, I cannot find any provision to keep the adapter plate from shifting on the back of the engine, i.e. dowel pins. Am I missing something here also?

Thanks
Joe H

[11SecAvanti]

The primary plate that bolts to the block should be dialed in for centering around the crank and then once dialed in, the plate dowel pins secure that centering to the block.

If you are lucky you can use the same holes in the block and drill the plate carefully for the dowel pin hole by using the engine block dial pin hole. It's a challenge especially on the full flow block. Some kits have a centering gismo for this plate in getting it centered to the end of the crank. I've seen the same snout problem. But just the opposite. The crank adapter hole for the snout converter was to small and had to open it for clearance.

Could be that various converters have various snout end sizes. I would just dove tail a sleeve to give the closest centering possible then slowly tighten up the converter bolts (one at a time with several rotations of the converter) until the final torque setting on the converter bolts. Good luck.

[Lanny Bertram]

Joe,
In the kit I installed last week the pilot bore is 1.705" and this issue is addressed in the instructions. The vendor offers to provide a different size bore in the adapter if needed.
My TH400 converter was too large so I opted for another converter because I wanted a differnet stall speed.
A centering ring was also provided to center the plate on the block. If you need a centering ring I can loan you mine.
Another issue I had is the gap between the flexplate and the converter mounting pad once everything is mounted. With the conv. pushed as far into the trans as possible the gap to the flexplate should be between .060" and .187". If it is greater than that shims may be used to reduce the gap.
--lanny--

[JoeHall]

Thanks for the feedback folks.

After research, 1.703" OD is the standard snout size on just about any TC made for any GM transmission (200R, TH350, TH400, 700R, 4L60E, 4L65E, 4L80E, etc.) going behind any GM V8, from 1970s to 1990s. It doesn't matter the source for the TC: AutoZone, Napa, ebay, B&M, TCI, etc., they are all the same. The snout size is determined by the size of the hole in the rear of the crank which, again, is same for 1970s-1990s GM V8s. Put another way, any 1970s-1990s GM, V8, TC with a snout size other than 1.703" is very likely custom made for a special ap.

So, in light of the above, the crank flange recess in any adapter kit for a Stude needs an ID of about 1.705", no matter which GM tranny is being installed. The vendor and I are in agreement, and are working on a solution to the 1.780" recess mentioned above.

In the archives, I read where someone had gotten a kit from Dave L. back in the day, and the hole was too small. But the gist I got from all other threads was they were dealing with holes too large: vibration, TC slop, etc.. One good thing, if the hole is too small it is near impossible to complete the install. OTOH, if the hole is too large, the install goes easy, too easy, and the problems come later.

As for the centering gizmo, which fits over the crank flange, it seems to be standard for all the GM adapter kits for Studes. It is a brilliant idea, is easy to use, and will no doubt center the adapter plate well within spec. However, unless I am missing something, this particular kit has no provisions for dowel pins to keep it centered, but I will come up with something.

Lenny, I am familiar with the gap between flexplate-to-converter pads, as you describe, due to having installed a TH400 behind a 352 in a 56J before. That's easy to remedy though, with flat washers.
In another thread, you mentioned not using the upper set screws/bolts due to distortion? If you would, please elaborate.

Thanks Again
Joe H

[Lanny Bertram]

Joe,
The 2 uppermost plate to bellhousing bolts were tappered head screws with the flat head facing the engine. The allen hole on the screws are partially coverd by the block.The screw heads had a slot cut into the radius. The set screws were drilled and tapped from the trans side of the plate to prevent the screws from turning when the nuts were tightened. The set screws were longer than the plate is thick so they interfered with a flush fit of the housing and plate.
In hind sight I could have ground them down flush (duh!).
Sounds like I had the larger (1.780") converter that you need and you have the 1.703" that I needed. You can have mine if you want it is going to scrap.

[JoeHall]

Hi Lanny,
Thanks, but I don't think your TC would do me any good, since it is not a lockup type.
Do you have a part number for it, since it came with the 1.780" snout? I cannot find a listing for anything other than 1.703" under anything GM from 1970s-1990s. I looked at website catalogs for Napa, AutoZone, O'Rielys, Dayton TC, etc..

Thanks,
Joe

[bige]

I bought my kit from Myer's and needed to request a "shim" from them after putting the whole mess together. They were nice enough to send it no charge after commenting that "they have never needed to use one" but I don't understand why it wasn't included in the first place. Now that I got that off my chest...it is simply a ring that makes up the difference between hub size and converter nose size. I'm sure you could purchase one from them or if you bought the kit from them all you should need to do is ask. It is ABSOLUTELY necessary as you will not be able to get that converter centered without it. The difference in smoothness is night and day.

Yes you are right about keeping the adapter from moving. Again, after things were bolted up and the car was driving I got home shut it off to use the key on the ring to unlock the shop door and when I tried to start the car the starter would not engage. Easy fix though...make sure the starter is lined up properly tighten the bolts, pick your roll pin size and drill a couple or a few, up to you, properly sized holes through the plate into the lower block where the adapter and block are flush and tap in the roll pins. Plate won't go anywhere from then on.

[bige]

One other thing...The shim was not wide enough so when the converter was moved forward it just sunk into the hub. JB WELD to the rescue. Attach the shim to the converter then assemble when the epoxy sets.

[JoeHall]

bige, I sent you a PM.

I bought my kit from Myer's and needed to request a "shim" from them after putting the whole mess together. They were nice enough to send it no charge after commenting that "they have never needed to use one" but I don't understand why it wasn't included in the first place. Now that I got that off my chest...it is simply a ring that makes up the difference between hub size and converter nose size. I'm sure you could purchase one from them or if you bought the kit from them all you should need to do is ask. It is ABSOLUTELY necessary as you will not be able to get that converter centered without it. The difference in smoothness is night and day.

Yes you are right about keeping the adapter from moving. Again, after things were bolted up and the car was driving I got home shut it off to use the key on the ring to unlock the shop door and when I tried to start the car the starter would not engage. Easy fix though...make sure the starter is lined up properly tighten the bolts, pick your roll pin size and drill a couple or a few, up to you, properly sized holes through the plate into the lower block where the adapter and block are flush and tap in the roll pins. Plate won't go anywhere from then on.

[Bill USN-1]

Joe,
Just a reminder that we may need to tweak some settings in the EFI chip if you are going to have the ECM do the TCC.
I would need to look yours up and see how we set it up initially.

[JoeHall]

Joe,
Just a reminder that we may need to tweak some settings in the EFI chip if you are going to have the ECM do the TCC.
I would need to look yours up and see how we set it up initially.

Hi Bill,
The chip you sent in the last HFI kit was so spot-on, right out of the box, I do not want to touch it.
Also, I decided to go with a 700R and TVC, versus a 4L60E and electronics. The TBI did give me a break with the TVC hook up, since it already had the connection for the cable, with GM's geometry already in place. I intend to run an OEM cable and just hook it up per GM specs.
I have no doubt though, had I went the 4L60E route you could have set the ECM up blindfolded

Thanks though

[Bill USN-1]

Joe,
I'm referring to that ecm controlling the torque converter lockup.
It was used in many applications with the 700r4 so it's just a matter of connecting the TCC wire through the brake light switch(only opposite) and then turning it on in the chip. That way there is no need for any external torque converter controller.
It controls the fuel, timing and the trans lock up.

The 4l60e/4l80e would require a different pcm since the trans is completely controlled electronically and not hydraulically like the 700r4.

Good to hear the system is working good for you.
HTH