Early GM NV4500 input shaft swap q's

[h82crash]

I don’t blame you for using the AA bellhousing. I was wondering as I am doing something similar although I got my transmission from a local transmission shop. It was supposed to be a ‘96+ case and my adapter from AA is PN 712576.

It turns out that my case is the earlier version with the narrower bolt pattern. I might drill and tap the bellhousing if I am not able to swap it for the right one. Did you order PN712577?

Yes I ordered the proper one, but as things seem to go for me, the one I need is backordered. The big hole in the bellhousing is called a register. The later GM NV4500s is larger and you cannot use it with the earlier bearing retainer. The alignment is critical for the input shaft, to the degree of .007", if I recall. You may be able to drill new mounting holes but, the transmission will not be aligned with enough precision. An alternative is finding or having an adapter ring machined to center the bell properly, but it would be pretty thin and still needing to drill mounting bolt holes.

 

[Mike Shull]

Yes I ordered the proper one, but as things seem to go for me, the one I need is backordered. The big hole in the bellhousing is called a register. The later GM NV4500s is larger and you cannot use it with the earlier bearing retainer. The alignment is critical for the input shaft, to the degree of .007", if I recall. You may be able to drill new mounting holes but, the transmission will not be aligned with enough precision. An alternative is finding or having an adapter ring machined to center the bell properly, but it would be pretty thin and still needing to drill mounting bolt holes.

Thanks for the information. I didn’t realize that the bearing retainer size was so important and I remember this being an issue when the transmission shop was building my transmission. I had them connect with AA and they assured me that they worked out the correct retainer.

Is it possible that they put the 96+ retainer on the earlier case?

I’ll have to do some research to find the size differences to see what I have, unless you know those sizes off hand?

 

[PIP]

Yes I ordered the proper one, but as things seem to go for me, the one I need is backordered. The big hole in the bellhousing is called a register. The later GM NV4500s is larger and you cannot use it with the earlier bearing retainer. The alignment is critical for the input shaft, to the degree of .007", if I recall. You may be able to drill new mounting holes but, the transmission will not be aligned with enough precision. An alternative is finding or having an adapter ring machined to center the bell properly, but it would be pretty thin and still needing to drill mounting bolt holes.

I'm a machinist and I solve these kinds of problems for a living. To me, this is a straightforward, affordable, minimally invasive fix.

redrill holes and machine a centering sleeve. The centering sleeve can be a shrink fit, or the preferred method would be to measure the chamfer in the bellhousing register and include a reverse chamfer on your sleeve that way it's an easy install, cannot inadvertently fall out and removes easy down the road if changes are needed.

I make a living doing this kind of repair work for a local community of around 100K people. A lot of areas have machine shops like mine. It wouldn't be a terrible idea to support that local infrastructure. I know I struggled for awhile until all the surrounding shop's owned by old timers closed up and I was last shop standing.

Just throwing it out there because too often people are trained to think that everything is throw away or must be fixed by a factory somewhere. I have to say the supply chain problems of today have brought me a ton of new local customers. Many of whom didn't think there were any local options.

 

[h82crash]

Thanks for the information. I didn’t realize that the bearing retainer size was so important and I remember this being an issue when the transmission shop was building my transmission. I had them connect with AA and they assured me that they worked out the correct retainer.

Is it possible that they put the 96+ retainer on the earlier case?

I’ll have to do some research to find the size differences to see what I have, unless you know those sizes off hand?

Look at the transmission. If it has an aluminum retainer with no guide tube sticking out the front then it is the later. If it is cast iron and has a guide tube, it is earlier.

 

[Mike Shull]

Thanks for the information. I didn’t realize that the bearing retainer size was so important and I remember this being an issue when the transmission shop was building my transmission. I had them connect with AA and they assured me that they worked out the correct retainer.

Is it possible that they put the 96+ retainer on the earlier case?

I’ll have to do some research to find the size differences to see what I have, unless you know those sizes off hand?

Update: I found the measurements and I have the 93-95 retainer size. AA sent me a 4.831 retainer so I’m not sure what the plan there was as it doesn’t come close to fitting the 5.025 opening in the bellhousing.

 

[Mike Shull]

Look at the transmission. If it has an aluminum retainer with no guide tube sticking out the front then it is the later. If it is cast iron and has a guide tube, it is earlier.

It looks like the earlier. It is magnetic and appears to be cast.

 

[h82crash]

Yes, early retainer.

 

[Mike Shull]

Thank you.

 

[h82crash]

I got my adapters.