pretty sure my crank is toast :(

[haywire4130]

i was looking over the crank and bearings on my recently disassembled motor and was quite alarmed when i saw the thrust bearing. the rear was worn so deep that the grooves were completely gone (it now measures 1.027 wide, yikes!!!) and the rear thrust surface of the crank where the bearing rides is nicely counterbored into the journal about .090 deep. my question is: since i don't have a new crank or good pictures to compare it to, is the "counterbore" normal or did it really wear that deep? when i place a new bearing on it, it has about an eight inch of slack fore and aft. i'm assuming this is the only part that regulates front to rear movement. i'm also assuming there is an issue with the converter or something that was forcing the crank forward? if that ends up being true, i wonder what kind of shape the trans pump is in...? i cant believe someone put it together like this! luckily i bought the car right but it's frustrating to do all the detective work and put out all the fires!

 

[ttaowner]

i have a std/std turbo crank here if you need one, other engine parts as well

 

[gndoug]

From what I have read/heard, many times when a trans is rebuilt the builder will modify the valve body to raise line pressure. This high line pressure will push your converter foreword, wearing the thrust bearing. If this is the issue, I believe the valve body can be removed and have a smaller orifice installed to lower line pressure. I'm sure someone with more transmission experience can chime in.

 

[haywire4130]

From what I have read/heard, many times when a trans is rebuilt the builder will modify the valve body to raise line pressure. This high line pressure will push your converter foreword, wearing the thrust bearing. If this is the issue, I believe the valve body can be removed and have a smaller orifice installed to lower line pressure. I'm sure someone with more transmission experience can chime in.

good info to know, kinda sucks there's not really any way to check it. i'm obviously gonna do some measuring when i reinstall the trans and go from there. it was replaced right before i bought the car and it is a hopped-up one so thats a definate possibility. that and i don't know the make/particulars on the converter either. i'll post pics in a couple weeks when i get to that point. this poor car has multiple multiple stab wounds, it's a miracle it even ran considering what was happening inside it! it was fast too! lol


tta: could you please pm me a pic of your crank and a price, as well as what part of ct you live? i'd be up for a road trip some evening after work. i'm weighing my options on going forged but i think that will be in the budget at the next tear-down... this leads to my next question: i'm gonna be asking a lot of this motor, do i need to balance your crank or can i just drop it in, in your opinion? i am running wiseco .030 over forged pistons on polished stock rods with a rjc girdle, shooting for mid 10's with a/c, not gonna be spinning any crazy rpms. the car came with a 10.6 time slip in it so with all the fires put out and everything fresh and properly tuned i think it's realistic.

 

[bison]

The crank needs to be replaced. The reason for the thrust failure needs to be pinpointed. Trans line pressure has little to do with a crank thrust that is shot. I run 275-300psi line pressure and never had a thrust failure. The converter pressure needs to be addressed. Ive seen modifications to the converter charge circuit that could result in high converter pressures unless the converter had mods to it to prevent it. To be safe id order a new pump assembly that has been modified for proper performance for your application. Id also check to see if the converter balooned out enough to press into the crank.

 

[haywire4130]

thanks for the info, the crank has been retired to "paperweight" duties. the converter thats on it is smaller than a d5, i haven't measured it, but it has a billet cover on it. i'm assuming that if it had ballooned and i installed the trans and then checked the thrust i would have zero? is this a common problem? by this, i mean is it common to wipe out the thrust surface so badly? i will try to get some pics of the converter tomorrow and then spend half the night learning how to post them. i really should have bought a stock car to modify!!!

 

[haywire4130]

also, fwiw cottons installed a "street strip 2004r" in it a few months prior to me purchasing the car, the reciept was in the glovebox. i would assume they use a reputable builder for their transmissions and that it should have been set up correctly for a turbo buick, so i'm thinking the converter is suspect... no doubt the car was beaten on after the install if that makes any difference. the previous owner was a hammerhead-

 

[haywire4130]

Update: picked up a useable std/std crank from James (ttaowner) who was kind enough to meet me at 11pm and show me his collection of strangely-optioned turbo buicks. I'm picking up the crank from my machinist shortly (chamfered holes and polished) and I'm bringing him my converter to inspect and hopefully identify hopefully we find a smoking gun so this doesn't happen again!

 

[haywire4130]

i took my converter to my machinist, he said it has anti-balloon rings and said it looked pretty beefy for what that's worth. he didn't recognize the make, i forget the exact numbers because it isn't in front of me but it is black and had CPT **** stamped in it, looks about 10" diameter with a billet cover.
had a friend come by this evening and he told me about a mustang engine that had wiped out the thrust in 80 miles. he said the crank had .0015" of runout on the center journals and that caused it to walk. so just for grins we put the old bearings in my block and dropped the old crank in and put a dial indicator on it. all journals were about .0005 to .001 except for number 1 which was .004 of runout! could this be the culprit? i put my new (used) crank in and checked it and it was nice and straight, .0005 max thanks again james, that crank polished out nicely, measures good and all my clearances were dead nuts!

 

[ttaowner]

your convertor is perhap california performance transmission ( art carrs new business) just guessing. glad everything worked out on the crank if you need anything else keep me in mind. thanks again