My 87 GMC Suburban Transmission only works on Low 1.

[Tony]

Hello Folks,
This is my first post. I need some help. I was driving along and felt and heard a rumbling noise. Then all of a sudden my burban wont go. I had to drop it to Low 1 in order for it to continue to move. I can go up to 20mph on D, then it just rumbles and stops moving till I get to L1. Any advice as to how bad the damage is. Thanks
Tony

 

[89Suburban]

Yikes.

 

[Jims86]

Yikes.

your going to need the transfer case rebuilt or replaced. just went through the same thing a year ago.

 

[89Suburban]

your going to need the transfer case rebuilt or replaced. just went through the same thing a year ago.

I thought he meant low 1 on the trans shifter, is it his transfer case he is talking about?

 

[Tony]

It is an automatic transmission. Thanks,

 

[Jims86]

woops, i thought you talking about having to shift the transfer case to low gear, sorry.
have you checked your fluid levels?

 

[johnmc]

tv plunger in transmission stuck out . Is the kickdown cable real lose?give it a pull and see if you feel the spring on the other end.sounds like its stuck on passing gear 1 gear.

 

[Tony]

What about the vacum modulator?
My neighbor thinks that could be it.

 

[HotRodPC]

Which transmission you got? Should be a 700r4 which does NOT have a Vac Mod. Shift points are determined by the governor and TV cable. BUT, I hate to be the bearer of bad news, but it sounds to me you've had a catastrophic failure in the transmisison. IF all you have is manually selected 1st gear, and no first gear in Drive, then your low/reverse clutch pack is OK, but I'll look at the graph and be able to tell you which clutch pack went. I'm thinking you lost your forward clutch pack and the trans will need to come out and rebuilt. Let me check some stuff out and I'll get back. In the meant time, any precise details you can give would help, like First in manual 1st and reverse are rock solid, nothing in 2nd and nothing in D, or any noises you hear, and at which point and what type of noise.

 

[Tony]

Thanks Hot Rod PC,
This is what happens; I start up the truck and am hearing some sort of vibration. I'm not sure if this has anything to do with it or not, but it settles down after a few seconds. I can put it in Reverse no problem. Then in Drive (with circle) it goes fine till about 15mph or where a shift should occur and just goes into what sounds like neutral. I can switch it to D and then it will go a little bit more but not much. I then switch it to L2 and it shifts to next gear and I can drive it like that. When I slow down i put it back to D for a little till the speed goes up and then back to L2. Hope this helps and hope it's not catostophic. Thanks.

 

[HotRodPC]

Hate to say it. It sounds toasted. Your low/reverse clutch pack and dirct clutch pack seem to be OK, but the forward clutch pack is likely the bad pack, and if this issue has heated up the 3-4 pack at all, which is likley, then the 3-4 pack is likley coned pretty good by now. Sounds like it needs to be pulled to me. Well see if Pops wants to give an opinion too.