When in D or O-D car won't accelerate beyond 25mph

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Originally Posted By: GreeCguy
Question: Would this be the 700R tranny or would it be either the 350TH or the 400TH?

Either way, as has been said, they are they cheapest and easiest to work on and rebuild.


This is a good question as the 700R4 is a 4 speed while the other two are 3 speeds. This would explain the linkage not making it to 1st.

OP can crawl under and check out the pan bolt shape and number of bolts and compare them to gaskets or ask professor google.

If you do get a rebuild, ask for a "corvette servo"-- they're $20 and make the shifts less mushy.

A 700R4 turns into a 4L60E in the early 90's when they got electronic controls via computer/ solenoids of the shifting. The 700R4 uses the TV/ kickdown cable up to the throttle body.
 
Hmm, that would be an important distinction, Eljefino. Crawl under, take some pics, and then compare with pictures on google?

The symptoms are the same as the Number 2 issue in the video I posted for the 4L60E except that I still have reverse, it is just a weak reverse. Perhaps the tranny has been replaced with a 350TH or 400TH, if that's the case then I would probably want to replace it with a 700r4 / 4L60E, right? Why would someone have put a different model in there?

@Memphis, I would think it has been changed, at some point in the past 26 years, but I am sorry to say I can't recall the last time. I read an article earlier about checking and changing Tranny fluid that said that some vehicles, namely newer models, do not have a drain valve. As this is an 88 I assume I could find a drain valve on the Tranny casing? Would I then go about a tranny fluid change about the same as an oil change?

@Rhymingmechanic, I don't think that's the problem. I've never had any issues(well, noticeable ones at least) with the shift being off in firmness. The only thing close to that is a few months ago it shifted from park to OD really rough, like a big "CLUNK" and a jerk, but then drove fine.
 
Yes if it has a drain plug on the transmission just like your oil change.

If you have the 700R4 it takes exactly 5 quarts from a drain and fill. I would try something like Supertech dex/merc high mileage or anything really dex/merc.

Heck throw a gallon of Maxlife synthetic dex merc and a couple bottles of lubegard red in there... Who knows?
 
IIRC, when the sun shell breaks the transmission will not have reverse, second or fourth.

It sounds like you still have reverse (maybe) and second.

From your description, it also sounds like you get up to 25mph and the transmission wants to shift into 3rd and it feels like neutral. This is a symptom of a burnt 3-4 clutch pack. This is a very common failure with this transmission. Once this happens nothing short of a tear-down will fix it.

If it's the 3-4 clutches that are bad, driving it in manual 2nd will not harm the transmission.

Whether it's the sunshell or 3-4 clutches, the transmission is going to have to come out and torn down to replace these items.

Based on the mileage that's on the unit, it's best to just have the trans rebuilt (if you decide to keep the truck). No need to get too fancy. Just a straight stock rebuild will do. The rebuilder should pitch the existing sunshell and replace it as SOP.

The new GM sunshells are an acceptable replacement. They're thicker and heat treated in the area of failure and are fine for a stock rebuild. Aftermarket ones are about the same money so it's a toss up, IMO.

Don't forget to add in the price of a rebuilt converter as well.

On a side note, the TV cable is NOT a kick down cable. It is also not used to adjust shift points. This cable controls main line fluid pressure based on throttle opening. Shift points are handled by the governor.
 
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I'm tempted to suggest either "Lucas trans fix," if the fluid needs to be thicker, or "Seafoam trans tune" if the innards need to be cleaned, and of course we all chant the mantra of "Lubegard."

I've had some pretty good luck with all three, depending on the condition and problems of the transmission.

But it seems the consensus here is that internal hard parts are broken or worn beyond resurrection and therefore, additives are probably a waste of time and money.

Even a simple fluid and filter change has the very slim possibility of bringing the ole gal back to life, if but for a short time. But if we're looking at a for sure rebuild in the very near future, why even do that?
 
Thanks guys.

So, for rebuild make sure to note:
Stock rebuild + a "Corvette Servo"?

@Paulo, what do you mean by 'replace the sunshell as SOP'? I am not familiar with that acronym.

My Tranny pan seems to match number 6 on this chart, meaning it is a TH700R4, 4L60, or 4L60E. According to dates of transmission advancement, I think it's safe to assume I have a 4L60.

If I do have the 4L60, which is a 4 speed, why does my gear selector not go to 1st? Could something have not been put back together correctly if it was previously worked on?

Tranny fluid level seemed fine, though it wasn't the reddish/pink I've read it's supposed to be. It wasn't pitch dark black either though. Unfortunately I didn't see any drain plug on the pan... Is it possible to get a tranny pan with a drain plug for the new tranny? That way I could change the fluid easier.
 
SOP = Standard Operating Procedure. In other words, something they would do as a matter of course rather than a possible option.

As far as a drain plug is concerned, I wouldn't worry about it. I don't have a drain plug on any of my vehicles and use a simple hand pump to pump the fluid out of the tranny via the filler tube. It works well for me and costs all of 6 bucks. I even replaced the orange plastic hose with a clear hose so I can watch as the fluid pumps out because I'm funny that way.
 
Do you have a 4WD or 2WD truck? Your mechanic will need to know that, because labor to remove and reinstall a transmission on a 4WD truck will almost always be more expensive than on a 2WD truck?

If you have 4WD, have you tried switching back and forth between 4HI, 2HI, and 4LO to see if anything changes? For all I know, a transfer case problem could be the problem, or contributing to an existing problem. I sure hope the transfer case is also in good shape, that would raise the price of repairs dramatically.
 
@GreeCguy, Ahh, right. I would expect all the parts to be replaced if it was a rebuild.

@Artificialist, it is 2WD. I would love to get a 4WD sometime but that would be my hobby and workhorse truck.
 
Just called my regular mechanic and he says he would get one from a Rebuild shop as opposed to him rebuilding it. Parts, Labor, and all would be somewhere in the area of $1800. That would include a 3 year/50k mile warranty from the Rebuild Shop.

How does this sound? Reasonable, gouging, or a good price?

I'm going to look into getting quotes from some of the other places around here as well, though I expect them to be higher.
 
Originally Posted By: JasonTL
Just called my regular mechanic and he says he would get one from a Rebuild shop as opposed to him rebuilding it. Parts, Labor, and all would be somewhere in the area of $1800. That would include a 3 year/50k mile warranty from the Rebuild Shop.

How does this sound? Reasonable, gouging, or a good price?

I'm going to look into getting quotes from some of the other places around here as well, though I expect them to be higher.
$1,800 is probably a little more than what you could sell the Suburban if it had a good transmission, unless it's in realllly good shape. Maybe sell it as is for $400 and spend $2,200 on something else. Just my opinion though.
 
Sounds expensive to me. I would call powersource with their 800 number and ask if they have your model. They sell a completely remanufactured 700R4 using the best practices in the business making it as good or better than new for $1299.

You would have to pay someone to install it but you get a 3 year 100k warranty and free shipping on your return core.

A rebuild could be a good one but too many chances that they re use parts that they aren't supposed to.

http://www.bestrebuilttransmissions.com/GMC.htm

If you 100% trust the shop and they can answer any question about which hard and soft parts get replaced, then local is easier.
 
Transmission fluid is cheap. Drain it and replace with the factory listed amount. Then you KNOW it's got the right amount in it.
 
Originally Posted By: 901Memphis
Sounds expensive to me. I would call powersource with their 800 number and ask if they have your model. They sell a completely remanufactured 700R4 using the best practices in the business making it as good or better than new for $1299.

You would have to pay someone to install it but you get a 3 year 100k warranty and free shipping on your return core.

A rebuild could be a good one but too many chances that they re use parts that they aren't supposed to.

http://www.bestrebuilttransmissions.com/GMC.htm

If you 100% trust the shop and they can answer any question about which hard and soft parts get replaced, then local is easier.


At 1300 dollars just for the unit, he still has to cover shipping, installation, parts and taxes. Sounds dangerously close to 1800 installed to me. Plus he'd be cutting the mech out out the $$$ loop, which makes it that much harder to pay his bills.
 
Originally Posted By: The_Eric
Originally Posted By: 901Memphis
Sounds expensive to me. I would call powersource with their 800 number and ask if they have your model. They sell a completely remanufactured 700R4 using the best practices in the business making it as good or better than new for $1299.

You would have to pay someone to install it but you get a 3 year 100k warranty and free shipping on your return core.

A rebuild could be a good one but too many chances that they re use parts that they aren't supposed to.

http://www.bestrebuilttransmissions.com/GMC.htm

If you 100% trust the shop and they can answer any question about which hard and soft parts get replaced, then local is easier.


At 1300 dollars just for the unit, he still has to cover shipping, installation, parts and taxes. Sounds dangerously close to 1800 installed to me. Plus he'd be cutting the mech out out the $$$ loop, which makes it that much harder to pay his bills.



Shipping is free both ways. Not sure what parts he would need, probably fluid only.

Even if the price was the same, which it isnt...Theres just too good of a chance the rebuilders will charge him for a rebuild, but just replace minimal parts, which makes the rebuild worth less.

I will say i am surprised by the warranty, i would run from any shop that offers only 12 month, 12k warranty.

I am debating both of these options myself, reman vs rebuild with my 4T65e, but my local shop who rebuilds transmissions has me somewhat confident that he can do a proper job. He had a good answer to every question on my laundry list, except his knowledge of fluid, which was [censored], but he offers a 3 year 36k warranty which is pretty good for a 4t65e rebuild.
 
Mechanic said he would get a new one from 'the rebuild shop', he didn't say the name of it. I could ask him about getting one from this place instead after I call them and see if they have one and how much it would be. The 3yr/100k is a bit nicer than the 3yr/50k he said the shop would give, although I doubt I'd hit more than 10k a year.

Memphis, would I have to pay the core-charge AND the $1300 upfront, or is the core part of that $1300, or do I get charged the core if I have no intent of sending it to them?
I assume if I did go with them then I would pay for it and have it delivered/the core picked up from my mechanic, or would the mechanic handle all of that?

If I were to judge that company by their website I'd turn away in an instant(Being one who does things with websites, theirs is...eh), however if a Carguy on here, especially a longstanding one, suggests them then I'm willing to check them out. I'll give them a call and ask, doesn't hurt, right? I assume the number is the one on their page.

Nick, if this was just a beater or simply a daily driver, I likely would. However I really like this car and have had other work done on it and plan to eventually restore it back to (better than) original.

I also intend to get at least one other quote from a place nearby.

Thanks for the comments and advice, guys. I appreciate the continued support.
 
Yeah i think you pay the core and $1299 upfront, and you return the transmission in the same crate they ship it to your mechanic in.

I know their website is cheap, but check out this video on their processes. Mostly about their engine process, but still shows you some stuff.

https://www.youtube.com/watch?v=qAwTpfGTCp0


3 year 50k warranty ain't bad. I think your transmission is a fairly durable unit compared to some since it's mechanical, (Less electronic parts to fail).
 
Today I drove it a bit and then parked it on flat terrain and cycled through the gears then shut it off and popped the hood. There was a wisp of smoke or something coming from the dipstick tube. I then pulled it, cleaned it, and put it back in and then quickly took it back out and it just barely read on the stick, so definitely low on fluid. The stick seemed to say add 1 pt(Pint), but shouldn't it actually be 1 qt(Quart)?

Anyone know offhand which fluid this vehicle takes?

Would low fluid actually prevent it from switching gears, or did the low fluid cause the 3-4 clutch pack to burn/fail?
 
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