5LM60 5speed Manual HELP

There are four GM medium duty transmission designs that led to and are often mistaken for the NV3500:

• 1987 MG-290 MG= Muncie Gear
• 1988 HM-290 HM= Hydramatic Muncie
• 1989 5LM60 (early)
• 1991 NVG 5LM60 (late) NVG= New Venture Gear
• 1993[1] New Venture Gear releases the NV3500. Externally the earlier GM units look like the NV3500; however the internal components were extensively redesigned.
  • The HM290 and 5LM60 units have a complicated arrangement of 4 shift rails. The NV3500 has one shift rail.[2]
  • There are two designs for the 5LM60 input shaft and bearings (input shaft and main shaft). The first design 1988–1990 has a ball bearing with a roller bearing behind it. The second design has a much larger single ball bearing. The first design bearings are reputed to be failure prone.[3] The updated input shaft and bearings carried through to the NV3500.
• All 5 of these transmissions can be interchanged as a complete unit with the following caveats.
  • "Drop-in" interchanges between GM S (S10 etc.) and C/K trucks will require modification of driveshaft length and crossmember placement. GM S models have a longer tail-shaft than C/K trucks.
  • Master & slave cylinder bore sizes went from standard to metric in 1992 (Master: 11/16"->18mm, Slave 13/16" ->20mm)
  • GM and Dodge transmissions will not interchange.
    • The case and bellhousing are one piece with differing, engine specific, bellhousing bolt patterns.
    • Dodge uses Dodge specific input shaft length, spline count, and pilot diameter.
    • Dodge output spline count differs from the GM units.

It is most likely a 5LM60

Due to the changes in these transmissions many parts are not interchangeable.

These are not easy to work on.

There are four design levels of this unit. It started in 1988 as an HM290 found in GM trucks, and was re-designated 5LM60 with early and late designs. Hm290 and 5LM60 units each have 4 shift rails. The unit was completely redesigned as a 3500 with a single shift rail. Due to all the design variations it is critical to positively identify which model trans you are working on in order to get the right parts.


NOTE: this transmission should not have 80W-90 fluid it. 80W-90 is to thick and will cause problems. These transmissions had a high rate of front bearing failure.

When I received training at the GM training center in Minneapolis in 1991 on this transmission. The training manual (which I still have) refers to it as a 5LM60 Formerly HM-290. At that time I was told the transmission was currently being built by New Venture gear and New Venture Gear is a joint venture between GM (Muncie transmission) and Chrysler (New Process Gear).

In 1987 it was referred to as MG-290 My guess is the G is for Getrag
In 1988 it was referred to as HM-290 HM= Hydramatic / Muncie
In 1989 it was referred to as 5LM60
In 1991 it was referred to as NVG 5LM60 NVG= New Venture Gear

There are two designs for the input shaft, input shaft bearings and main shaft bearings. The first design, which documentation will show as 1988-1990, had a ball bearing and a roller bearing behind it. The second design only has a ball bearing but it was a much larger bearing. The first design bearings were more prone to fail. They were failing when these trucks were under warranty with very low miles on them.

There is no way I would suggest fixing your transmission. The bearings are very expensive. Last one I did an estimate on, it was over 2 hundred just for the GM input bearing. The input shafts are different so you can’t put the better bearing in the earlier trans. Also if you take apart the main shaft, many of the parts cannot be reused, and you need an oven and melt sticks to heat the parts to the correct temp for pressing them together during reassembly.

A large holding fixture (special tool) is used to hold everything in position when assembling the transmission.

It is almost always less expensive to replace these transmissions then it is to rebuild them. Even in parts prices alone. It is hard to find good used ones.