Transmission shudders

[LMP]

80 km/h is the speed near which 4th gear is applied under light to moderate load conditions...Under light acceleration, TCC applies during 3rd gear, then when 4th is applied, it can be felt as a light thump, as a solid mechanical link is already establihed; slight changes of throttle position will release TCC whe going uphill, and it can apply again as speed increases or load is decreased, all of this being felt normally as small thumps; light degradation in the transmission internal organs, seals, accumulator O-rings, can increase the thump...but beside the annoyance, this will not degrade the transmission components. Since the T60 Hydramatic is by nature an extremely smooth transmission, any degradation is quickly noticeable.
IN OD, transmission shifts under light acceleration are 1,2,3,3TCC, 4TCC
WHen in 4TCC, a sudden increase in throttle position or loss of speed going uphill will drop from 4TCC to 4, then 3 if it keeps slowing...then back to 3TCC and 4TCC when gaining speed slowly, or from 3 to 4 then 4TCC under harder acceleration.

[blazes9395]

What is the milage on the transmission? Is it original, or has it been rebuilt before? That bump you mention sounds like the torque convertor locking up adruptly. The transmissions used in these years(4T60E, 4T65E and more) all had problems with valve body wear causing all sorts of problems. While the transmission itself, and the convertor were almost always alright, they were slowly destroyed as a result of the worn valve bodies. The valve body in a transmission basiclly controls of the transmission function(gear shifting, torque convertor lock-up etc) from signals it gets from the PCM(vans main computer(Powertrain Control Module)). Tranny shops are very reluctlant to just change the valve body in a transmission, as usually when valve body issues pop up, there has been damage internally anyway. They almost always rebuild it.

My advice at this point is to get another transmission service as soon as possible, don't flush it but get someone to drop the transmission pan, and change the filter and replace the oil. I would defiently add the LubeGaurd, and make sure you use good quality transmission oil, not the bulk stuff lube shops use. Valvoline would be my pick as it is formulated to help reduce shudder in transmissions.

Good Luck, and let us know how it goes.

[Laura H]

You guys are amazing but now I don't know whether to feel optimistic or not. I just had to go out for a few minutes and drove in 3 rather than D and there was no bump at 40K. I'm not out of the city very often to get much over 60K but I can try it on the weekend. It was just Friday that I had the flush done. Are you saying that I should go back again and remove the pan and replace the oil? I'm not sure I understand what the purpose of doing that would be. I'm liking the explanation that a small thump is normal, but I'm worried about missing something crucial. It's 98 Pontiac Transport and no, the transmission has never been done. It's got about 165000K. It's had regular maintenance, brakes done a couple of times, replaced leaking rear wheel cylinder in 2004, had something major done in 2004 to do with S/gr rem and a steering rack leak (very expensive), power steering flush in 2006, $1500 worth of something else done in 2006 to do with the pressure line and return p/s lines, new water pump in 2003 and again in 2008. I have one bill here also from 2006 to do with the transmission. The bill says that "shifting very harshly". Tech comments were "check for trans has max line pressure check for vac at modulator and find 18 inches. remove heat shield and modulator and check for modulator valve being stuck, is ok. reassemble and find is working ok again". I think I remember that this was after they had done some other work, and it ran worse after. I think they messed up and had to fix the mess.

[96tsport]

Was the tranny flushed as in hooked up to a machine & power flushed?

[Laura H]

I think so. I don't know if you're familiar with the Great Canadian Oil Change or not but that's where I had it done. You stay in your car and he did roll up a machine to it that said "transmission flush" on it.

[96tsport]

Would you know if the tranny pan was removed & the filter changed? Or when it may have been done prior?

I ended up asking in this forum about a power flush & finding out there is alot of controversy out there about the procedure & different ways of going about it. One concern with a flush is debris going through sensitive parts of the tranny & making problems where there were none before.

Generic tranny fluid that may have been used by the shop can also be problematic.

I think that's why the suggestion (from blazes9395) to drop the pan, change the filter & put in a known quality oil as something you cannot go wrong with at this point & pretty sure is the factory recommended way of going about it.

However, if the filter was changed at the flush, probably just changing the oil is fine. Some folks might say the only filter to use is a GM filter.

[Laura H]

If that isn't standard procedure, then I don't know. But I could find out. The flush was to try to correct the problem - it didn't create it. Maybe I sounded like it did. Sorry.

[blazes9395]

Originally Posted by 96tsport

I ended up asking in this forum about a power flush & finding out there is alot of controversy out there about the procedure & different ways of going about it. One concern with a flush is debris going through sensitive parts of the tranny & making problems where there were none before.

Generic tranny fluid that may have been used by the shop can also be problematic.

I think that's why the suggestion (from blazes9395) to drop the pan, change the filter & put in a known quality oil as something you cannot go wrong with at this point & pretty sure is the factory recommended way of going about it.

Exactly.

I generally don't mind flushes, as long as they have been done on a regular interval. If the transmission hasn't been serviced regularly, a flush can "shock" the transmission as a result of the tendenancy for the new fluid to clean the internals of the tranmission and sending debris throughout the tranny. Bulk fluid from lube shops also tends to be the cheapest stuff out there, I am not a fan of lube shop bulk fluid at all.

Just like 96tsport said, I suggested a pan drop because you'll have known good fluid in there, and a new filter eliminating a possible clogged filter too, even though the flush was just done, thats fine. It sounds redundant, I know, but it may do the trick.

Also as for the vacuum modulator, very common on these trannies for this part to not function quite properly. This modulator is located top drivers side of the transmission, facing the front. These tend to wear, or the vacuum coming from the engine(engine vac line) tends to get restricted or clogged, casing poor control of transmission line pressure. This little modulator which is about $40 or so caused a many 4T60's to burn up and need rebuilding.

[PDESORM]

The famous shudder...
Had it on my 93 Trans Sport for almost a year. Usually happened going uphill or on a slight corner. It magically went away after I replaced plugs, wires and the 3 coils AND the plate (module?) underneath. I got the module set at a scrap yard for about $50.00 CAD. Make sure it is WELL bolted down. A bad connection will keep it from working. I had no more shudders since, but I did retire the Green Machine this year. I have 2 '93s for sale for parts or to fix. One runs great.. except it's frame is kind of rotten.
Phil.

[Laura H]

You are all awesome! I wish all of you lived next door. I really appreciate all of the info and suggestions, and will print it off and take it tomorrow to the GCOC guy to see what he says. I've been driving in 3rd the past couple of days and haven't noticed the thump at all. Not sure what that means or even if I would understand it. Here's hoping I can get one more year without any more huge bills. My next vehicle has to be a mid-sized pick-up (used) - any advice on what lemons to avoid would be taken to heart.

[LMP]

Originally Posted by PDESORM

. I have 2 '93s for sale for parts or to fix. One runs great.. except it's frame is kind of rotten.
Phil.

..too bad this machine that looks so great from the outside gets ruined from underneath. I started seeing that proiblem with mine. Living in northern country, salt is a common presence in winter and this is just apalling. I now keep mine in a garage for winter, that is, at rest from november til May 1st...hoping to extend its useful life. I have a Kia SPortage for winter...and it's taking a toll....

[jeffroso]

I have a Toyota Highlander that was running great. Took it to Jiffy Lube and had transmission fluid replaced and now the vehicle shudders while I'm driving. Could they have messed this up?

[blazes9395]

This is not necessarily the right section to post this queston, but for the Highlander, you need to use an approved fluid, and not a generic fluid that Jiffy Lube most likly put in. First don't drive it like this, you run a risk of damage. The fluid to use would be a Toyota T-IV fluid or equilivant. Amsoil, Mobil 1 Synthetic, Redline D4, all are very good equilivants and should get it operating normally. You need to flush it now, to make sure you get all the wrong fluid out.

[jeffroso]

Thank you for the advice on the Highlander transmission fluid. I came that close to telling Jiffy Lube no, but went for convenience. Lesson learned!

[kawtool]

Originally Posted by Laura H

Thanks so much for the reply. I checked with the place that did the transmission flush the other day and he said, yes, the torque converter would have been flushed as well. So I guess I can cross that off my list. It seems that I may be wrong in calling it a shudder. He says that a shudder would continue for some time, but what I feel is more like a bump or a thump, almost always at 80K going uphill. It also sometimes happens at around 40K but not always. He has suggested driving in 3rd instead of D to see if it makes a difference but to keep an eye on the rev's. The vehicle runs fine other than this annoying "bump" which I can live with if I knew for sure that it isn't doing any other major damage by driving it. My emergency credit card can't afford a new transmission right now. Thanks for any help or suggestions.

Laura H,
I have been having the same symptoms as you had with my 1998 Trans Sport, 3.4 L, 320,000 km. It started in the summer and first thought it was an ignition issue and changed plugs and wires. It still continued and I took notice when this stumble, feels like you hit a crack on the road, occurs and mostly about 80 to 85 kilometers per hour and more pronounced going uphill. Once past that speed range or under the van runs smoothly. Trying to get through this winter with this van so what have you done with your problem after this posting. Same as you I can live with this annoyance, have been for a while. I wonder if this is the speed and rpm when the transmission kicks into overdrive?
Hopefully you see my reply and inform me.
Thanking you in advance,
Kawtool,
Toronto, On.