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Damage caused by too-thick torque converter?
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Author:  Reed [ Tue Jun 01, 2010 10:09 pm ]
Post subject:  Damage caused by too-thick torque converter?
What damage would occur to a 904 lockup tranny if someone installed a torque converter that was too thick?

I ask because I replaced the torque converter in the junkyard transmission I installed in my brother's van and it was noticeably wider in diameter and about 3/4-1 inch thicker than the torque converter I installed. Tomorrow or the next day I will be tearing the transmission apart to inspect the internals and I need to know what to look for.

Assuming the old torque converter was too thick, what internal damage would be caused by forcing it in place? When I installed the fat converter it was a VERY tight fit. I assumed the van transmission used a larger torque converter. Was I wrong? :(
Author:  Fopar [ Tue Jun 01, 2010 10:29 pm ]
Post subject: 
You must have damaged the front pump by forcing the converter into place. Don't know of a thick or thin converter only have lock-up or non lock-up. When fully engaged in the transmission, you should have about 3/4 of an inch to pull the converter forward up to the flex-plate after the trans and motor are bolted together.
Author:  66aCUDA [ Wed Jun 02, 2010 4:42 am ]
Post subject: 
Reed
If it was forced you will need to look and the rear main oil seal on the engine as well. I have even seen in extreme cases damage to the thrust bearing.
Frank
Author:  Doc [ Wed Jun 02, 2010 8:22 am ]
Post subject: 
The slots in the hub of the converter, will bottom-out on the pump's impeller, pushing the impeller hard against the rear of the pump housing and wearing that surface.
The thrust bearing in the engine can also be damaged, as already noted.
DD
Author:  Reed [ Wed Jun 02, 2010 8:57 am ]
Post subject: 
Crap. That makes sense though. The transmission now does a nasty whine on startup unless I shift into neutral. Once the engine warms up, I can start the van and the transmission doesn't whine.

It was very odd. The big converter barely fit into the bell housing of the tranny, and barely fit behind the flex plate. It was wider and thicker than the stock converters. That should have told me something, but I recall reading somewhere that trucks and vans got bigger converters? I must have been wrong though.

I really hope I didn't mess up the thrust bearing in the motor. So far, no leaks from the rear main seal, but I will look closely when I pull the transmission.

At least I have another lockup 904 I can steal the pump from.

Sounds like whoever rebuilt the tranny and put it in the van I got it from in the junkyard put in the wrong torque converter. I used that torque converter because it was the one in the tranny at the boneyard.

Thanks for the input. I will go pull the pump out of my spare tranny, check all the clearances, and cross my fingers. Every place I call wants $1k to even touch the tranny. One place wanted $750 to replace the torque converter. These people are nuts.

I am hoping that the thrust bearing in the motor is OK since the transmission actually worked fine for several months before it started shuddering right before kickdown around 37 MPH.

I swear, this van is cursed with transmission problems. Or maybe I am just cursed with bad transmission luck.
Author:  volaredon [ Fri Jun 11, 2010 8:56 pm ]
Post subject: 
you won't like my suggestion but take it for what its worth; quit playing w/904s and put in a 727, and your trans trouble will diminish. I, too, tired of swapping 904s just to have more trouble down the road; when I started going to 727s my trans problems all but went away.
Author:  Reed [ Fri Jun 11, 2010 10:27 pm ]
Post subject: 
Been there, done that. We bought this van in about 1999. I pulled the original 904T transmission that was working fine because of a leaky front pump seal. My brother decided to go with a 727, so we got one and put it int. It lasted about a year, then died. He had it rebuilt a,d it lasted a couple months before dying again. Then my brother parked the van for about five years in a storage facility.

A few years back, he dug it out and wanted to get it on the road again, so he droppped it off and I swapped the tranny for ANOTHER 727 that Eric W gave me. This one worked for a while, but eventually developed problems. So out came the 727 and in went a 1979 904 that sixshotvanner gave me.

That 904 worked great, until my brother blew one of the rubber hoses coming off the tranny before the metal cooling line started. He fried that transmission REALLY good, so I ended up pulling the current 904T out of a junkyard a few months back.

Currently, the van and the junkyard 904T are at a transmission shop since I am tired of dealing with it. :wink:
Author:  Charrlie_S [ Sat Jun 12, 2010 5:09 am ]
Post subject: 
How did you wind up with a "too thick" converter? As far as I know that can't happen, unless the converter was made incorrectly. In that case the rebuilder should be responsible for the damage. I had that happen on a V-8 904 race converter. The builder made it for use with a "block plate", which I wasn't running. That resulted in the converter being 1/4 inch too long (thick), and it ruined the front pump. The converter people repaired the converter, and totally rebuilt my trans, at no charge. I did have to remove the trans, myself.
Author:  Reed [ Sat Jun 12, 2010 7:35 am ]
Post subject: 
The "too thick" converter was in the transmission when I bought it from the junkyard. I have a sneaking suspicion that the van was at the junkyard because of the converter and the damage it caused.

No matter. I bought a new correct size converter and the trans is at a shop being fixed.
Author:  slantzilla [ Sat Jun 12, 2010 1:27 pm ]
Post subject: 
Sounds like you might be better off to get a new brother. :D
Author:  Reed [ Sat Jun 12, 2010 4:03 pm ]
Post subject: 
No comment.
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