This is for Transman - If He's Still Around - And Any Other Transmission Guys

riviera
buick
transmissions

#1

The car is a 1990 Buick Riviera. 3800 Pre-Series I V6, 4T60 transmission. It JUST developed this problem tonight.



As I am accelerating, the car feels normal with plenty of pull and no excess slippage off the line and through first gear.



As it shifts OUT of first gear, the shift is very SOFT, it’s always been fairly soft. But then it seems to just kind of come down and lock into second, bit of a clunk, not too bad, can pass it off as less than a small pot hole.



Coming out of second she shifts even softer, freewheeling with a noticible loss of drive for about a second, maybe two, before starting to lock down into third. It comes down into third with about the same speed as a newbie shifting a manual and letting off the clutch, and has the same feel, except it lets out this profound shudder which feels and sounds exactly like when you drift too far to the side of the road and hit the rumble strips. But once it’s in, it feels normal.



Out of third and into fourth is normal. Transitions into lockup as normal too.



And lastly, there is a squeak. Never happened before tonight. Definitely associated with the second gear and third gear shift. Also seems to make its presence known while cruising along in high gear, TCC locked. It may do it all the time, but it has come correlation (volume and frequency) to that second and third gear shift.



So what happened?

I’m no newbie and I know a bit about transmissions but I’m certainly no pro. I figure maybe a clutch/band burned out in the transmission and that’s rebuild territory. But also maybe I lost something else. I don’t know, as I said I’m no pro. But I’d like to know what’s wrong, not just “yep, sorry buster, rebuild time.” If that’s possible. I can handle some technical, if it starts to sound like gibberish, I’ll post back and ask “what the heck did that mean?”



I appreciate the help!



-Matt


#2

Update:
I drove it about 20 miles this morning.
It seemed to not do its thing EVERY time. Almost every time, but once or twice I couldn’t detect any abnormality in the shifting.
I also noticed a bit of a rumble going into second, like the one going into third. But that was only maybe every other time.
Sometimes it’d also make the grinding going into third but there’d be no momentary partial loss of drive, it’d just plow through, so to speak.

No leaks that I can see.

-Matt


#3

Matt,

Doubtful that the 1-2 band is going to be an issue. It is already applied in 1st AND 2nd gear. If it was slipping, you would notice it in 1st as well as 2nd. Age is probably affecting the piston seals in the 2nd and 3rd clutches. Have you looked at the modulator yet? Another issue we had with the 440T4 was damage to the 1-2 shift valve. It was actually bottoming out in the valve body and getting damaged. The 1-2 is an aluminum valve so it damaged easily. Usually that would cause a lazy 1-2 shift or 2nd gear starts. Can you get to a pressure guage for some line pressure tests??

transman


#4

I know a shop down beachside that does transmission rebuilds on their bench. The guys there have been doing cars for a long time. I think they might be able to handle a pressure test/diagnostic.

I haven’t encountered a second gear start yet. She’s gone about 60 miles since I first encountered the problem (I thought I had ran off the road because of the shudder.) I ended up turning the wrong direction down some god forsaken road and ending up two towns over, bass ackwards with a questionable transmission. =(

I’m going to have the shop take a look at it tomorrow if they can squeeze it into their lineup.

I’m wondering if I can get at any of the aforementioned parts/seals for replacement/rebuild from under the trans, through the pan. I’m also wondering if there’s a POSSIBILITY that you have maybe more than one 4T60 service manual kicking around that you could mail me??? I know that’s asking alot but I figured nothing could hurt by throwring it out there.

Also, I remember you reccomending some chemical in a red bottle for transes with problems. Is that, or maybe a can of Seafoam TransTune, something that maybe can rectify this problem, or atleast forestall final judgement?

And finally, if I have to have this transmission town down and rebuilt, how much should I expect for the work? And how much for a used/rebuilt 4T60 and where can I get one?

I know I’ve bombarded you with questions/requests but you do not know how much this piss poor college student appreciates any help/advice you can offer.

Sincerely,
-Matt


#5

Modulator passed test.
Had adequate vacuum supply.
Fluid level and condition are okay.
Not great but okay.
How about that Lube Gard stuff, will it help me?

-Matt