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Old 07-17-2009, 07:06 PM   #1
Free88
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1991 Sillverado 5 Speed trans problem

Today while driving on the highway something went crazy with the trany. I went to down shift from 4th to second for a stoplight and the gear shift just seemed to float wherever it wanted. It took some time to find 1st gear to pull away from the stop light. After finding the correct gear and making sure of the position of the gearshift handle I went to shift to second and slid into 4th. After some playing around i was able to get it shift again but when I went to back up it would not go into reverse. After a lot of pulling an pushing on the gear shift I got it into reverse and backed in. There seems to be way to much travel in the shift handle. Is this a sign of a worn shift fork or something broke in the trany case? Thanks for the help an suggestions in advance.
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Old 07-17-2009, 09:31 PM   #2
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Re: 1991 Sillverado 5 Speed trans problem

If it is the original 1991 transmission it is referred to as NVG 5LM60
NVG= New Venture Gear

People will call your transmission a NV3500 which it is not.

The 5LM60 has 4 internal shift rails is much more difficult to work on then the NV3500 which has a single internal shift rail.

The 1991 transmissions were superior to the 1988 to 1990 design but are very complicaed to repair

There are four design levels of this unit. It started as a 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.

There is no way I would suggest opening your transmission. 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.
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Old 07-17-2009, 10:34 PM   #3
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Re: 1991 Sillverado 5 Speed trans problem

Chevytech, thank you. I have the original build sheet for this truck. I just looked up the option code for the trans and it is MG5. Description calls it a Manual Transmission 5-speed (Getrag). It also says MM5 Transmission manual 5-speed Provisions (Merchandising Option) 5-speed M/Trans (MM5). Both numbers appear in the RPO Description Detail sheet. I do not know if this is helpful but I thought that i would post it as it differs from the ones that you listed. Any more help would be appreciated.
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Old 07-17-2009, 11:28 PM   #4
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Re: 1991 Sillverado 5 Speed trans problem

You’re welcome!

MM5 - MERCHANDISED TRANS MAN 5 SPD PROVISIONS

MG5 - TRANSMISSION MAN 5 SPD, GETRAG, 84MM, 4.00 1ST, O/D

This fits the 5LM60 but I think that MG5 was also used in other years with the other designs of this same transmission group.
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Old 07-17-2009, 11:52 PM   #5
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Re: 1991 Sillverado 5 Speed trans problem

Thanks. So when I go to look for a transmission do I look for one that says Getrag or one that says 5LM60?
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Old 07-18-2009, 08:11 AM   #6
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Re: 1991 Sillverado 5 Speed trans problem

1993 New Venture Gear released the NV3500. Externally the earlier GM units "look like" the NV3500 however internal components were extensively re-designed.

I would look for a NV3500 for a replacemnet out of a newer truck.

Note: All the illustrations in the 1993 service manuals are of a 5LM60, with multiple shift rails, so I don’t know when they switched to using only the NV3500 in production.

I would stay away from anything built before 1991

Remember from the outside these transmissions look alike.

Sorry – I have not saved any identification number information for identifying them.
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Old 07-23-2009, 07:03 PM   #7
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Re: 1991 Sillverado 5 Speed trans problem

Well I got brave today and took out the four bolts that hold the shifter on. It lifted right out and out fell a pin that looked like a nail head. There was also a piece still in the trans. Took these too parts out, but not sure where they are supposed to be. the pin is about 3/16 inches in diameter and has ahead on it about 1/4 to 5/16 of an inch. Looks like a nail. The length was about 1 1/4 long but it looked like it had a cotter pin slot in it because the one end was rough and looked like it was drilled. Does any one have an exploded view of this trany that could post it for me? I looked in my 91 service manuls and it does not show an exploded view of this trany. Thanks
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Old 07-23-2009, 09:18 PM   #8
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Re: 1991 Sillverado 5 Speed trans problem

Take a look at this but it does not have much shifter detail.

http://www.drivetrain.com/parts_cata...ustration.html
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Old 07-23-2009, 09:32 PM   #9
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Re: 1991 Sillverado 5 Speed trans problem

It really does not show much detail as to the part I am talking about. When the shift lever was pulled by removing the 4 bolts on the top on the trany this piece came out and a part of it remained in the trany which was removed with a magnet. Looks like the head of a nail. IS there a parts list that coinsides with this diagram?
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Old 07-23-2009, 10:10 PM   #10
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Re: 1991 Sillverado 5 Speed trans problem

You could try digging around that site and see if you can find a list, but I don’t know if it has one.

If you give me the number of the part on the illustration, there is a good chance I can give you the name it is called.

Look up it the pivot area of the sifter and see if the part you found came from up there. That would be my guess.
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Old 07-23-2009, 10:21 PM   #11
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Re: 1991 Sillverado 5 Speed trans problem

The closest I can get too for the area for the nail head pin came from would be the part that number 61 goes into. This part, if I am not mistaken stayed on the end of the shift lever when it was pulled. I will get the pin in the morning and post a picture of it, as well as where I found it. Thank you
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Old 07-24-2009, 08:27 AM   #12
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Re: 1991 Sillverado 5 Speed trans problem

The parts in number 61 in the illustration from top to bottom:
Snap ring
Washer
O-ring
Shift socket bushing
O-ring
Shift shaft socket

There should have been a cylindrical shaped piece that stayed on the bottom of the shift lever when it was removed. Did that come apart?

I have not found a good illustration of the pivot area on the shift lever. What you found could be the part that keeps the shift lever from rotating. Does the shift lever rotate more then it normally did?
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Old 07-24-2009, 09:13 AM   #13
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Re: 1991 Sillverado 5 Speed trans problem

Yes the gear shift rotates all over. I should have mentioned this earlier, it might have not caused so much confusion,
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Old 07-24-2009, 09:28 AM   #14
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Re: 1991 Sillverado 5 Speed trans problem

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Yes the gear shift rotates all over. I should have mentioned this earlier, it might have not caused so much confusion,
There is probably nothing wrong with the transmission. What you found is most likely part of the pin that keeps the lever from rotating. With this problem it is hard to tell what gear you are it and where you are shifting to.

Disassemble the shifter that you removed and look for a broken off pin where the lever pivots.
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Old 07-24-2009, 09:41 AM   #15
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Re: 1991 Sillverado 5 Speed trans problem

I had hell with a shifter issue in the same transmission not too long ago, call these guys - 1.800.788.9120, and explain to them what you have and what's going on and they will fix you up. I searched for two weeks getting the proper shifter and parts for the 5 spd in a '92 c1500 2wd I had and they fixed me up, and did it quickly. i wish I could remember the guy's name I talked too, but just let them know your issue. They had extensive knowledge of this transmission.
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Old 07-24-2009, 06:04 PM   #16
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Re: 1991 Sillverado 5 Speed trans problem

An update on the shifter. Thanks for all the help and links. Living in the small town that are in parts are very limited. We measured the pin and it was .131 of inch. We tried and measured many objects and the closet we could come to a nail shaped pin, yes a nail. I went to the building centre and picked up a 7 inch spike. Measured it and it was .132 in and off I went to the garage. we measured the length added a touch, took a die grinder cut it off, rounded off the edges and it slipped into place. Shifter is back on and shifts smooth. I know this is not the best fix but when your in a pinch, any redneck idea may work. I am now on my way to the city to the scrap yards looking for 5 speed transmission that I can get a couple of these pins to have on hand. Again thanks to ChevyTech and anyone else who helped, it was much appreciated.
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Old 07-24-2009, 06:28 PM   #17
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Re: 1991 Sillverado 5 Speed trans problem

Baling wire; duct tape; vice grips; all have a use and it isn't always as designed. I'm gonna guess that the pin that you needed is like a clevis pin. It's probably hardened and what you have will probably wear more quickly, but a mans gotta do what a mans gotta do. I once tied a tie rod end onto the spindle with a shop towel. It got me home, okay?
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Old 07-24-2009, 06:46 PM   #18
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Re: 1991 Sillverado 5 Speed trans problem

Never tried the rag to hold on a tie rod, but used silicone and duct tape to repair a rad to get me home once.
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Old 07-24-2009, 08:35 PM   #19
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Re: 1991 Sillverado 5 Speed trans problem

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Originally Posted by Free88 View Post
An update on the shifter. Thanks for all the help and links. Living in the small town that are in parts are very limited. We measured the pin and it was .131 of inch. We tried and measured many objects and the closet we could come to a nail shaped pin, yes a nail. I went to the building centre and picked up a 7 inch spike. Measured it and it was .132 in and off I went to the garage. we measured the length added a touch, took a die grinder cut it off, rounded off the edges and it slipped into place. Shifter is back on and shifts smooth. I know this is not the best fix but when your in a pinch, any redneck idea may work. I am now on my way to the city to the scrap yards looking for 5 speed transmission that I can get a couple of these pins to have on hand. Again thanks to ChevyTech and anyone else who helped, it was much appreciated.
You are welcome!

Glad to hear of your progress, and thanks for sharing what you have found.

Nails are not bad metal and are harder then many other steels. Take a look at the governor weight pivot pins on the turbo 350 transmissions. I was told by an instructor when in trade school that they were finish nails.

If you are having no other issues with the transmission I would keep using it. Now if I could find a NV3500 cheap, I would buy it for a back-up. I call all my STUFF inventory. Grabbing another shifter would be easy.
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Old 07-24-2009, 09:59 PM   #20
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Re: 1991 Sillverado 5 Speed trans problem

Quote:
Originally Posted by ChevyTech View Post
.......I call all my STUFF inventory....
ChevyTech, I never considered that terminology before. I don't know if the bride will buy it, but I'm gonna start using it. Lets see how long it takes her to figure it out......

By the way, I wanna say how much I appreciate your help that you have offered so many people. Thanks!
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Old 07-25-2009, 10:18 AM   #21
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Re: 1991 Sillverado 5 Speed trans problem

Quote:
Originally Posted by ChevyTech
.......I call all my STUFF inventory....
Quote:
Originally Posted by ChevLoRay View Post
ChevyTech, I never considered that terminology before. I don't know if the bride will buy it, but I'm gonna start using it. Lets see how long it takes her to figure it out......
My wife quickly pick-up on my reference to my hoarding of parts and now tells others of my “inventory” and that it is cataloged in an access database. And yes, she and many people think I am a little to organized.

Quote:
By the way, I wanna say how much I appreciate your help that you have offered so many people. Thanks!
Thanks again for your ongoing sharing of appreciation.

Many here seem truly thankful.
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Old 07-26-2009, 11:19 PM   #22
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Re: 1991 Sillverado 5 Speed trans problem

Just a quick note to let you all know that the spike trick worked great in the trans. It shifted smoothly and had no problem at all. Off to get a couple more and make up some spares. Thanks again for all the help ChevyTech.
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Old 07-27-2009, 06:51 PM   #23
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Re: 1991 Sillverado 5 Speed trans problem

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Just a quick note to let you all know that the spike trick worked great in the trans. It shifted smoothly and had no problem at all. Off to get a couple more and make up some spares. Thanks again for all the help ChevyTech.
Excellent, and you’re welcome!!!!!
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