NV4500 Buyer Beware

[gert]

I have found out the hard way buying a transmission that someone cobbled together..... there are differences in the NV4500 that makes somethings not interchangeable:


Early model GM 92-94 transmissions have a 6.34 first gear and a 6.34 reverse. The bolt pattern on the front is the same as a SM465, this bolt pattern is different than the 1995 and up. The Gear set will not be interchangeable with the latter case. The reason is in the reverse idler gear and counter shaft size necessitated a 2 3/8 long idler gear which changed the shape of the the case:

Early model Look at the protrusion behind the pto cover and compare it to below: (also notice early style cover/shifter style)



Late model 95 and up the protrusion is smaller to accommodate the shorter idler gear on the 5.61 reverse gear: (notice bolt on shifter like late model transmissions, the cover IS interchangeable between cases)



this is what the early counter shaft and idler gear looks like, the counter shaft gear teeth do not go all the way the the back of the case to clear the main shaft reverse gear:



Late model 95 and up: notice the full tooth counter shaft and shorter idler gear: ( notice the one piece counter shaft compared to the 2 piece pressed together early counter shaft)



this is what happens when you mix and match: I could not see this when I bought my transmission because the main shaft gears covered it up and of course it wouldn't spin I thought it was do to it not having the rear main bearing installed. The seller told me the 5th gear was burnt out and he decided not to rebuild it after it was at his transmission re builders shop.Well it was actually do to the idler gear crammed against the reverse gear:



When you are shopping for an NV4500 know the differences. i hope you have better luck than me. I was specifically not looking for the 6.34 geared transmission. I simply measured the bolt pattern on the front of the trans and looked at the gears and overall condition of the trans and thought I had what I wanted a 5.61 geared Chevy input 2wd trans. well not was all as it seemed I found part of one anyway

 

[gert]

So the main difference in the early case is the extra room inside the housing to accomodate the longer idler gear which can be seen on the outside by looking at the driverside rear of the case. The protrusion should look like the case shown, notice the black line drawn on the case




the reason for the longer protrusion is to make room for the 2.375" long idler gear do to the low 6.34 reverse gear there are no teeth on the counter shaft at the back of the case




95 and up 5.61 gear case has a shorter protrusion to work with the shorter rverse idler gear




Also the bolt pattern for the bellhousing is different. I plan to add the extra holes on my early case so that it will have both bolt patterns. I looked the cases over pretty good and it looks like the front faces are the same

 

[gert]

Been gone awhile, had a baby in the ICU and am still catching up from that. In the mean time the early reverse idler gear was discontinued. I made a few calls and to my amazement 2 different rebuilders on Craigslist said they had used gears. So I got to the police impound yard of all places as fast as I could and scooped up the last used part I need to complete the build of my trans so you can see the big difference in length between the two. The inside diameter is larger on the early style so the bearings won't interchange either.


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