Thread: Why does it bump

Sorry no GPs today, but if it's any consolation I did have a '64 421 4bbl many years ago.

Anyway our '04 Impala has begun to act up. When starting off from a dead stop or slow roll under average middle-age throttle application occasionally it will "bump" into gear (feels like a stick would if you let the clutch up too quick but just short of chirping the tires).

The wife tells me if it does happen, it typically happens within the first 10 minutes of driving. But the other day it acted up toward the end of a 3 hour highway trip when we got into some traffic.

I'm hoping this will be fixed painlessly before it fails completely, as our nearly identical '00 Impala had the trans done twice in 30k miles. That's my car now so for the time being it's safe and should last a good while longer. Both of these cars were 2nd hand from her mother who only drove them to the Casino on Sundays and went regularly to the dealer for $ervice.

From what you're describing it sounds like TCC lockup wich would be normal. But as far as the bumping i'm not sure.


And other details on what is happening?

Thanks Trannyman.

OK... I have more info now. The wife told me it *is* pulling the car when the "bump" happens. I have not verified as I almost never drive the car, but riding in it when it acted up, I suppose that is possible (what she says now) even tho it seemed to be grabbing into gear. Is that the TC lockup? Doesn't feel quite like the TC lockup in 1st that would happen with a 350-C on a V8. It's much harder & quicker.

I used to do a good bit of automotive work. But as could be expected, getting married, buying a house and having a kid ruined all my fun. Now many jobs are farmed out to the garage due to lack of time. And as such, costs have increased by an order of magnitude.

As for 4T65E experience, in the 2000 Impala,
#1 failed at ~80k cost $3k to replace.
#2 failed at ~110K cost another $3k to replace.
So MTBF = 55k miles
We're now at 135K miles with $6k into the tranny = $0.04 per mile overall cost of 4T65E ownership
But since it had 80k on it when we got it, and the 4T65E failed within 2 weeks, our cost of ownership of the 4T65E is $0.11 per mile.

We bought the '04 with 88k in September, maybe put 5K on it, and the cost of 4T65E ownership looks like it may be recalculated soon.

I did own a 1990 Bronco II 4x4, with which I did tow a 4000# boat trailer a couple of miles per year, and it did have an A4LD, which failed twice at about 80K and 130K miles. It had around 20K when I bought it. The first one got a bench job at the A place for $800 and did R&R myself. The beauty of the non-transverse mounted engine is evident here. When #2 failed, I replaced it with one from a 93 Exploder for a cost of $400. 6 years after giving it to my dad he still drives it with probably 160K on it now.

So A4LD MTBF = 65K miles
Cost of ownership = $.01 per mile.

I'm not quite convinced the 4T65E is a better transmission, just a more expensive piece of crap. But such is the nature of business to get things to market as quickly as possible, at the lowest cost. If the warranty is 36K and it lasts 37k then they're covered. In my most recent experience, both GM & Ford have become quite adept at zeroing in on the 100k planned obsolesence mark (about 120K when everything starts to break).

Originally Posted by DanGTP

My question is: "Who did the rebuilds on the two transmissions you have gone through?". A properly rebuilt & reworked 4T65E (like one from Dave the Trannyman) can last much longer than a stock one like mine. Also, how hard is the car driven?

I'm no transmission expert by any stretch of the imagination, but a 25K failure on a rebuilt transmission sounds like it wasn't maintained properly in its previous life and most likely wasn't rebuilt properly, either.

For the first job, they put in a Goodwrench unit (the one lasting 30k). The second one, was done by Aamco, it still works. We bought both the cars from my mother in law. She's one of those who drives the speed limit, buys all the extended warranties, and goes in for service fearing the car will explode if she does not. Unfortunately for us, she sells them right about when the warranty expires. We will NOT be getting the next car because it is a Hyundai.

We are fairly easy on them as well. The most severe service the 2000 had was that for about 8 months I took it 65 miles each way to work which amounted to the best part of an hour running up near 80mph provided I was not stuck in the NJ traffic. That was on the Goodwrench unit. These days we probably put less than 100 miles a week on each.

Aside from this expensive transmission issue, the cars are excellent IMO. I always had RWD V8s and these chassis are extremely well balanced for FWD although I do miss the throttle out of a curve. It is a tight car - very well put together. Better than my 60k 91Supercoupe, I reluctantly admit. Even with 135k on the original shocks the 2000 still feels pretty good although the '04 with just 90k is noticeably tighter. The 3800 series II is remarkable as well. Ample power, quiet and smooth. the 25mpg+ is all right too. The disposable plastic intake manifold was an unfortunate choice, however.