Not 100% sure, but I believe the 4R70W transmission in my '57 is slipping. Occasionally, when cold, it'll hesitate a bit when starting out at normal acceleration. It's just a momentary hesitation, seem to grab ok after that. No noticeable slippage at driving speed, but it may explain my drop in gas mileage in the past year or so. Yesterday, after driving 125 hiway miles home from a car show in Lubbock, when I stopped at some lights in town, it seemed to have a longer hesitation when taking off again.
So opinions....sound like a rebuild is in the future (urgh!!!)? Maybe adjustments or other remedies that can be done with the tranny still in the car?
With my health, this could be a major problem............trying to find a reputable shop that would be willing to work on a street rod may be a big problem. Dropping the tranny out in my garage is not a possibility........lol easier to pull the engine.
Just a suggestion but thats a fairly late model trans that any good trans shop should be able to diagnose for you.
I've got a really good trans shop near my house that I've used a number of times in the last 20 years. Very busy shop, I'm just not sure he's going to want to fiddle with a rebuild if it needs to come out. The issue is going to be getting at the top two bolts on the bell housing without pulling the engine forward. When I replaced the engine a few years ago, I pulled the engine and tranny forward a few inches to get to the bolts. That's a lot of work to just get the tranny pulled.
Next question. This is really going to show my ignorance, but................I've got the Yukon trac-loc setup with the clutches, etc. Could it be an issue with the that? I honestly don't know if both wheels are clutch engaged, or just one.
You could take the clutches out of a limited slip and it will still move...just won't spin both tires.
I know the bell bolt pattern is different than the Y-Block pattern but won't the access holes in the floor be close?
I would do some in car diagnostics. It sounds like it might be a control issue...lots of little sensors and solenoids. If a clutch pack was slipping a year ago, it would be torched by now or getting worse in a hurry. A hesitation sounds more like a sticky solenoid. Most control issues can be addressed without removing the transmission. At least it is cheaper to start there.
I took it out for a spin this afternoon. No hesitation at all, but it has always been intermittent. I'm kinda hoping, as you said Gary, it just needs some in-car maintenance work. I even got on a lonely stretch of road today, stopped, and nailed it. Just dug in and went. Even seemed a bit faster than I remembered. The car actually seemed to run much better after that, maybe just needed a "blowing out". Gonna go talk to my transmission guy tomorrow.
Thanks Jim and Gary for your input.
I'm going to guess that with your interior lay out accessing those two top bolts on the bell housing from the inside of the car is out of the question? There were two holes in the top of the tunnel (rubber plugs) to access the top two bolts in my Ranchero, (now used to run the engine compartment wires out), not sure if they were in all cars?
Pretty sure they're not accessible,Bill, but I will check if it turns out the tranny has to come out. Lol, lots of stuff under that dash, mainly the Vintage Air and computer stuff. Not sure how they would line up with my bellhousing bolts though. I've still got the old 4.6 sitting in my back yard (yeah, Redneck I know), so I can get some reference points for the location. Mainly, the console may be in the way.
Just remembered......somewhere I have a pic of the engine out/ tranny in that will give a good idea of how the bolts lineup with the holes.
We always used very long extensions and swivel sockets to get the upper bolts from behind the trans. Can't remember any that we couldn't get. Can't say about this installation though.
On reflection I do remember there were some vehicles that we had to remove trans crossmember and lower the rear of the trans to get enough access.
That's a possibility also. I'd just have to remove the throttle body and EGR valve that are too close to the firewall.
I did talk to my tranny guy today.......(lol, I'd better stop calling him "tranny guy", that's a whole different meaning nowadays). Without it actually doing the malfunction while he's driving it, which ain't going to happen unless it gets worse, he's not convinced it's the transmission. He said it's possible it's not downshifting all the way into 1st gear when coming up to a full stop. I'm going to drop it off after I get some $ and have him do a full in-car maintenance on it.
Just an update......hasn't missed a beat in another 1k miles, so I'm going to assume it wasn't a transmission problem.
Good news and hope the issue doesn't return anytime soon.