Replacing 4T60E - Do I have to drop the subframe?
 

Hi guys, my 4T60E in my 1997 LeSabre has been nothing but problems since I got the car with 23,000 original miles (that my grandfather put on it). I had the valve body intermittently cause a hunting O/D malfunction and had to be replaced around 30K miles, and now at 68,500 miles the TCC will repeatedly start unlocking pretty violently under load while going up a significant hill. I found a used trans with 31K miles for $425 with converter and I'm going to install it myself. I've done lots of muscle car era engine and transmission builds myself, but this FWD stuff is fairly new territory. My Haynes manual says I need to support the 3800 with a hoist, unbolt the motor mounts, and then separate the subframe from the suspension and drop it completely. Is it really necessary to drop the subframe to get the trans out and in? I always see junkyard 3800 FWD cars with the transmissions missing and the engine and subframe still bolted in, obviously people are getting these transmissions out without dropping the subframe. Can I come in from the top with the trans, or drop it from underneath? If its going to be more of a hassle installing the trans underneath through the subframe than its worth, I'll just drop the it, I know this transmission is very awkward and seriously heavy.

Sorry for placing this in a Bonneville forum, but this car is identical to a Bonneville other than the body skins, and this is a tech question I'd like to get some feedback on.

There's numerous posts on this topic that can go into more detail than I can right now (not in the best state of mind right now), but TCC shudder under load like what you're experiencing is often caused by an engine misfire under load, not TCC related. Make sure that it's not an engine problem before you throw a transmission at it.

Thanks for the quick reply. I strongly suspect that this is the lockup unit going out. I never have any check engine lights or stored codes. The car cruises fine in O/D at all load conditions until the car has been warmed up driving for 20-30 minutes -- then pulling hills at light throttle, especially long, steep hills, will start causing the trans to have some serious shudder issues with the lockup. The transaxle has developed a whine from 20-40 mph and the fluid is starting to smell burned. Most of the driving the car sees is normal highway driving, but I do drive aggressively the rest of the time. The 4T60E shifts great but doesn't seem to be built to handle anything other than Buicks 63 year old average audience puttering around with it.

It's easiest to drop the subframe. And I really have no idea how you would get the tranny out the top.

I put a trans in my bonne a few months ago......9 hours of actual work and a cas and 1/2 of beer and we had'er licked.....And that's with out a hoist and stuff....Hardest thing about this process is that these cars have a bolt that opposes the rest of the bolts going into the block that you need about 4 ft of extenstions and can only get to it from the right front fender well....Other than that...these cars are REAL easy. I dunno ANY way you can get these bastards out the top....but if you can do it, more power to ya and we want pictures!!! lol.

P.S. Where are you from?? Are you in MN or close to? I want your old trans if you do live close enough for me to pick up.

Nate

Lakeville, thanks for the input. Can you elaborate on how you dropped the subframe and changed the trans without using a hoist (I'm picturing lots of jackstands or a floorjack supporting the engine, which scares me). If I can avoid using a hoist that will save me having to drive 4 hours each way to borrow my friends. I go to school at Villanova, but will be working on the Buick at home in CT.

By the way, you can't use my 97 trans in your 95, 97 is a one model year only trans as far as interchangeability. Plus I may rebuild the old one and install a limited slip somewhere down the road.

have you checked to see if the VSS is working properly?? i dont think that through a code if it has failed i would seriously get that checked out 1st before moveing on with the swap

Game over, wouldn't my speedo malfunction if the VSS was acting up? The trans fluid is obviously burned smelling, and the tcc shudder only happens when the car has been driven for a while, like more than 15 miles. The only problem I've had with the car otherwise is that the tachometer has been intermittently not working when I first start the car, then after driving a few miles it will start working erratically and then be fine. I've heard this problem could be caused by crank position sensor. However, the time when the tach doesn't work does not correspond to when the trans is acting up. I'd think if I had a miss caused by a faulty crank position sensor that a) it would throw a code and b) it wouldn't cause a miss only after 15 miles or more of driving. But, I am planning on changing the crank sensor before I touch the trans.

1997_LeSabre,

I dropped the subframe on a '91 Sable using a heavy rectangular steel tube across the top of the engine bay to support the engine as the subframe was lowered. The car had to go up pretty high to provide sufficient clearance. I plan to do the same when I change out the 4T60E in my '95 SLE in a couple of weeks.

Now, having said that.....I'm not saying that your transmission is good, but.....

The symptoms you describe have been posted by many and are typically NOT transmission related. I know, your fluid is burned, etc. But others have been fooled by this engine trans combination. I had the same trouble you describe that turned out to be a cracked spark plug. It acted EXACTLY as you describe. It did not set a code. I have been working on cars for many moons, and I would have sworn it was a bad trans.

You might at least take the car to a reputable trans shop and get a free test-drive.

it was worth a shot