1989 K2500 Manual 5-Speed question... please help

[Benfromsac]

So I bought this single cab longbed truck a year ago and broke the reverse gear in the 5lm60 manual transmission. I opted to rebuild it myself since my budget was pretty limited at the time. It was a difficult rebuild, but I got it done and back in the truck. It wasn't a perfect job either, because now its giving me problems again. This is a work truck that routinely sees a lot of heavy work with about 150 miles a day.

My question is... am I able to take out this 1st production run getrag290 with the bad bearing design and do a clean swap with the improved 3rd run NV3500 w/out needing to do any modification? (my budget has improved lol) I would preferably have the NV4500 with the cast iron case, but I'm pretty sure that unit won't mate up since it was introduced a couple years after my truck was manufactured. I really want to keep the 5 speed instead of an automatic.

Any advice and tips would be greatly appreciated. Bear in mind that I'm pretty mechanically inclined with tons of tools and a nice workshop, but I am not able to fabricate or machine anything, so anything too complex is out of the question..

 

[dave_erald]

The easiest solution would be to find an entire donor truck that very nearly matches yours (i.e. same engine) and pull everything flywheel rearward.

Very nearly any chevy engine and chevy transmission pre 98 will bolt in pretty near any combination. Subtle differences will be found in shift linkage or flywheel design or clutch hydraulics blah blah blah.

In heavy duty applications you could get the NV4500 behind the 350 TBI and Vortec, in later years as long as it was an 8-lug truck it got a NV4500 for a manual regardless of engine size.

Our resident 5 speed guy should be chiming in anytime...



...pokes @Justin S with a moderate sized stick

 

[Benfromsac]

I believe this was a "light duty" 2500 since it has only 6 lugs. So you mean tranny, Xfer case, drive shaft and rear axle?

 

[dave_erald]

In all likelihood, yes.

Depending on the length of one transmission to another, rear driveshaft for sure will be different, as well as trans mounts and trans crossmember. I can only say based on what I've seen and what i've heard, hopefully we can find someone that has done this exact swap

 

[Justin S]

4L60E swap! I mean.... Yes, an NV3500 would be a direct swap. The older ones used the external slave setup, which should swap right over from the 5lm60 and the newer ones used the internal, I prefer the external because if something happens to the slave you have to pull the trans. I used to tow quite a bit with my old 1500 with the NV3500 and it never gave me any problems. My current 2500 has the NV4500 and it's great for towing, but I prefer the gear ratios of the NV3500 for everyday driving.

 

[Benfromsac]

4L60E swap! I mean.... Yes, an NV3500 would be a direct swap. The older ones used the external slave setup, which should swap right over from the 5lm60 and the newer ones used the internal, I prefer the external because if something happens to the slave you have to pull the trans. I used to tow quite a bit with my old 1500 with the NV3500 and it never gave me any problems. My current 2500 has the NV4500 and it's great for towing, but I prefer the gear ratios of the NV3500 for everyday driving.

I prefer the external slave as well. But the real question is, can a NV4500 be swapped into a truck that was made before it was? (without major modification)

 

[dave_erald]

96 and earlier NV4500's were external slave correct?

Get a flywheel and clutch for a 92-94 350 (assuming your engine is a 350) with the NV4500 and a 96 or earlier NV4500 and bolt the new stuff up.
Right?

 

[Chewy1576]

I swapped an NV4500 from a 1992 K2500 RCLB directly in place of an SM465 in a 1990 K2500 RCLB. Only thing swapped was the transmission itself. Flywheel, clutch/pressure plate, SM465 slave cylinder, NP241C transfer case, rear driveshaft, and transmission crossmember fit perfectly to the NV4500.

I started by researching transmission dimensions and specifics. I'm not sure about the 5LM60, but the SM465 and NV4500 shared the same input shaft size, output shaft size, and overall length was only different by 1/8" so the original driveshaft would work. Shift tower distance from the mating surface on the bell housing was nearly identical. While the SM465 slave cylinder worked, the bore sizes between it and the NV4500 slave were slightly different so I ended up swapping out the master and slave for NV4500 matching parts.

I went the parts truck route, and gambled by putting the NV4500 in without having it inspected first. Within 2 years, I have spent nearly $3000 between price of the parts truck, replacing the throwout bearing/shift fork/master and slave, and a full rebuild because bearings and synchros were worn out. If I were to do it all over again, I would buy a reman unit from www.highgeartransmissions.com, new flywheel/clutch/throwout bearing/shift fork/master and slave, and you'll probably be under $2000 with brand new everything.