Early GM NV4500 input shaft swap q's (1 Viewer)

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EDIT: SOLVED. See edit at the below.

I have researched this thoroughly and found conflicting info. Not that I have a strong desire to do it but I'd like to know if it is an option. I will be building my FJ40 soon and running an LM7, NV4500, to the FJ40 T-case.

Have a 93 GM NV4500 4wd with roached input drive gear and counter shaft driven gear, so both need to be replaced. Counter shaft gear should be separate and replaceable for this transmission. If I replace it with a 38t 4th gear I should be able to use a 22t input later GM shaft, as someone else has done with a Dodge shaft. I've read so many statements that it can't be done. but it seems like it has been done in this thread. (Although this swap was early GM with HD Dodge input shafts. But, if that was possible, then going to the 5.61 GM shaft should be even easier)

I understand if I swap the whole counter shaft, I'd be looking at a myriad of gear issues, so we don't need to discuss that.

Am I missing something?

The thread where someone has "done" it. Early GM MT4 NV4500 Behind a Cummins

EDIT: I contacted staff at Torque King and they verified my deduction. Here's a quote, "Most of these cases are the same as far as how the gears go in. So as long as you match the gears that mesh together with each other it will swap. People do this all the time."
 
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I haven’t looked into it farther then reading that everything needs to match, either everything matching 5.61 input, or 6.34 input. No experience here on changing ratios, just swapping GM/Dodge but both were 5.61.

Just curious, why not replace with the same parts and keep the 6.34.

Also, i will be selling a used NV4500/16-spline FJ40 AA adapter setup in about two weeks if you haven’t bought one yet.
 
I haven’t looked into it farther then reading that everything needs to match, either everything matching 5.61 input, or 6.34 input. No experience here on changing ratios, just swapping GM/Dodge but both were 5.61.

Just curious, why not replace with the same parts and keep the 6.34.

Also, i will be selling a used NV4500/16-spline FJ40 AA adapter setup in about two weeks if you haven’t bought one yet.

I'm not set on changing ratios, but the replacement early stuff is less plentiful. I know everything needs to match and that you just cannot swap to the later counter shaft without replacing all other gears. But since the gears on the early shafts are removable, and the correct tooth count large gear is also available, I can't think of a reason that prevents the the particular swap I described. But, you're correct. 5.61 is already a granny and the 6.34 won't make much difference when starting in 2nd while daily driving it.
 
Ive been down this road. I don’t deal with mixing and matching any more.

Allstate Gear should have all the replacement parts for your transmission
 
Well Allstate is out of stock on the 20t input. So, back to installing the 22/38 combo? Anyone? (I know there are other vendors)
 
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If anyone else has this question, it is yes, it will work just fine. See edit on first post.
 
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Well, Got the gearbox apart today. All the research for not. It has the guts of a 95 GM transmission already inside it.
 
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Ok been here,. The 95 gm nv4500 is an oddball, the front input shaft bearing/race is like the 92-94 transmission,. The rest of the case is like the dodge transmission. I have a 95 gm nv4500 behind a Cummins,. The dodge input shaft went right in but the bearing retainer is different. The inside register is smaller on the early transmission,. The later input bearing retainer register can be machined down for the later belhousing. The 96 and later bearing retainers have a bigger belhousing register same as the dodge.. if you need more info let me know..
 
Thing is, this was probably a 95, but it has the early cover with the round shifter, making me and the guy who sold it to me think it was a 93. Got all the parts and have finished the rebuild.

NV New parts.jpg


NV4500 complete.jpg
 
Nice Work, transmission parts on the dining room table??, if you get the end play right nv4500’s are real quiet and smooth… when I was looking for info on 95 gm transmissions they are a mixed bag as you figured out. which sincro’s did you run..?
 
Thanks. Yes, cold and dusty in the barn. Did the work in my neighbor's garage. I got the factory style carbon lined synchros in a kit and most parts from Trans Parts Warehouse. It came with Koyo bearings. Had to get shims and some missing synchro struts from other vendors.
 
I know it's expensive for what it is (highway robbery) but run Synchromesh aka the correct fluid. It will shift alot better and the synchro's will last longer.. most of the nv4500's I have seen with problems had the wrong fluid..
 
Thanks. I bought Red Line MT-85. It is the recommended fluid by Torque King. Many import transmissions now run the same synchro material and the proper lubricant is more common even though Castrol stopped making it.
 
If you do change the input and counter gear to the other ratio in any style of NV4500 it throws off all the other ratios. It's a significant difference.

I built a Cummins one with the short GM bolt on yoke once and used the early GM overdrive gears. It ended up with a massive overdrive, like .5:1ish. It was unuseable. Going the other way makes the overdrive around a .9:1 so equally as useless.
 
If you do change the input and counter gear to the other ratio in any style of NV4500 it throws off all the other ratios. It's a significant difference.

I built a Cummins one with the short GM bolt on yoke once and used the early GM overdrive gears. It ended up with a massive overdrive, like .5:1ish. It was unuseable. Going the other way makes the overdrive around a .9:1 so equally as useless.
I knew it would, but that is significant. I had a .59 in a built T5 and it was only good over 75 MPH. Had to change that 5th out. It might be ok if you had say, 5.88r/p?
 
@h82crash, what bellhousing are you running with this?
I'm waiting for the AA bellhousing. I know I could have done something else, but to drill and tap the transmission case to save a few bucks wasn't the answer. Also, the GM bells for this transmission that I did find were almost the same cost as the AA unit.
 
I'm waiting for the AA bellhousing. I know I could have done something else, but to drill and tap the transmission case to save a few bucks wasn't the answer. Also, the GM bells for this transmission that I did find were almost the same cost as the AA unit.
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?
 
Boy this is going back 20 years for me, but IIRC, the front of the case where the bolts holes are is identical regardless of which bolt pattern you have. Meaning you can drill two holes and it works fine. If the bellhousing isn't available I wouldn't hesitate to properly locate and drill the holes.
 

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