turbo 400 causing engine front bearing failure?

None of this has explained why it's eating the FRONT bearings in his engine.

 

uuhhhh........maybe he misspoke??

Ray

 

I think you are correct Ray it is the internal pressure pushing on the torque converter that is causing the engine bearing failure and the only real cure is the internal mod. described above. I for one am taking out the offending trans and taking it to my tranny guy for the mod. before I ever drive the vehicle with the new 454 it is in.

Gary

 

More proof. I took another look at the 454 I took out of the motor-home. As you can see by the pictures the crank has been pushed forward with much force. There is a space between the crank throw and the block. The front of the engine is on the right. And there is some bluing on the crank throw behind the cap.

 

One last comment I forgot, remember a flex plate is just that. Allows some flex movement to help prevent eating the thrust. Ive been thru this problem with some SFI tagged flexplates. Theyre too stout, and dont flex enough. A stock steel one for a street car is the best.

 

Good point.


Also too much clearance or wear at the pump gears can cause problemes with the thrust bearing, even in stock applications.
And also a restricted cooler or cooler lines.

 

If one want's to get a visual experience regarding the dynamics involved, pull the dust cover on a T-400/350/700r what ever and with a trust worthy assistant behind the wheel, take a position on the ground curb side with a flash light keep an eye on the flex plate when assistant places trans in reverse and power brakes up to 1500 rpm. You will be astounded and amazed!! The discription of 'flex plate' will take on new meaning. The deal is reverse boost pegs the line pressue up ward and the high line pushes the converter out of the pump. Line pressue is read @ 1/8" pipe port on road side center of case, lube oil/converter charge requires tapping into lower cooler line. We build a lot of performance/race application 400's so the pressure deal is a daily experience on the dyno. Information gained resulted in redesigning the pump inlet/filter arrangement. Specifically faster pressure recovery on full throttle up shifts, quicker shift,less slippage. If more people would take a drive with a trans pressure gage tech lines would get fewer 'dumb' questions.

 

restricted cooler circuit

 

Yep - remember the BALOONING issue on motorhomes - it was indeed balooning in this case, and only on motorhomes, and somewhat common. I remember the fix as a heavy duty converter - called an "Allison" converter, so probably diesel. But later 400s were not a problem - even with 502s - so the factory must have fixed it in later transmissions. I'm remembering this from motorhome magazines in the day - surprised not more of the tranny guys on here don't remember the specifics - but I have never heard about except with motorhomes. I suspect the original problem could be best fixed with a new, stronger converter.

 

Many guys think a converter will balloon under torque and snap back to shape when unloaded. NOT. What's more the proper splined bore to manipulate to check thrust clearance is the turbine bore. The one all the way in the front or at the bottom with converter horizontal. Thrust in excess of .030 is cause for concern. Hard to determine with out proper tool, coat hanger don't cut it. I've seen some real early 400s with a lube circuit by pass like all glides and 350s have, other than that there's been no change to that fluid path 400s until they were phased out of production, as in NO cooler bypass in 400s. Just to be clear, blocked or restricted cooler will result in loss of lube oil and greatly increase pressure in converter. I know of one guy who ate up 7 or 8 thrust bearings in his rat motor drag car before the light came on in his little world.

 

You learn something new everyday
Good tech/thread topic with an interesting outcome and fix.


.

 

Thanks guys keep them coming. I'll now invest in a new trans cooler and put a stock flex plate back in. The original owner thought he was doing the right thing beefing up everything.

And thanks moefuzz if for nothing else your avatar.

 

For everyone, Mike is the guru of transmissions. Whatever he says , do it.Hey Mike, I hang with your friend and mine, Marty B. The only guy that blew up more stuff than us!

 

Thanks Mike and everybody

Bottom line I'm taking out the tranny in my motorhome next week and taking it to my tranny guy who said he has done the mod. described on page one before. Would you do anything else to the trans? The trans I'm sure has a shift kit installed. Would you have that taken out? There is a new and I'm sure heavy duty flex plate. Would you remove that and put in a stock one? I'm going to replace the cooler radiator with a new one. What one would you suggest. I don't want this to happen again.

Thanks again Gary

 

Because your going to restrict the converter feed your also restricting the lube oil.
And because it's for a motorhome he could do the full time lube modification.

 

If it is a Transgo shift kit not meant for a towing/motorhome somethings should be corrected.

And if it B&M shift kit i would definitely remove it,

If the flexplate is a stock heavy duty type just use it.

Plate type coolers are the most efficient.

 

A little late to the party, but one more for restricting the converter feed hole in the front pump.
We wiped out the crankshaft thrust surface on the 454 in my buddys OT '72 Camaro race car, had he converter checked out and it was fine.
He found a tech sheet (not sure if it was a GM service bullitin or not) that mentioned this mod in regard to motor homes. Our usual tranny guy called bullshit (hes pretty stubborn when it comes to change) but we put in a restrictor anyway. No thrust bearing problems in the last 4 years since the restrictor and the car has run a best of 9.67 @ 145.

 

It really amazes me how many trans guys don' t believe in this restricter mod. when I talk to so many people who say it solved their problem.

 

And Mr. 4 sp gets a balloon. Restricting converter feed will reduce lube volumn. Not a problem with cars but can be a big problem for RVs and the like.

 

Another balloon for Mr. 4 sp. The .080 dia. wire regulator spring frequently requires reworking the governor to prevent 2nd gear starts. The SS units that come out of my shop boost pressure with an extra horseshoe spacer, thats all. Stock plates work well for heavy duty applications. The B&M type plates are fine for SS. Regarding the pump mod pictured and discussed as the fix, it's ONE way to reduce excess volume to the converter, BUT not all applications are the same and it can reduce LUBRICATION volume to the gear train too much, not always but it can. I would not assume a race car mod is the ticket for a tow rig, some guys can't tell the difference.
Those that are interested should pay attention to my remarks posted up stream concerning ballooned converters, greatly misunderstood issue.

 

Thanks Mr4Speed for your "bottom line" suggestions. From the Netherlands? Isn't the internet and the hamb great.

Never too late chop32. Glad to hear the restricter mod. worked for you. I hope I have as much success with it.

And thanks again to you Mike. Not sure I know all you are talking about but hope my tranny guy will. Gary

 

I dont pretend to be a transmission guy, but I do see where Mike is coming from...maybe there is a happy medium for sizing the pump restrictor for a motor home application?
The only other trans related thing Ive seen that causes a thrust bearing failure is a ballooned torque converter...I know they make converters with anti-balloning plates for racing applications, not sure about a low stall speed motor home application.
Good luck, and let us know what your tranny guy has to say.

 

I gotta repeat myself. Ain't the hamb great. I got a problem and I get help from maybe 10,000 miles away and 50 miles away and all in-between.
Thanks guys Gary. The trans is out and at my tranny guy who I told to read and get all info from this thread he can.

 

More pictures. Just pulled the rear main cap. You can see the damage. and the difference in thickness of the thrust surface. Hard to see but wore the crank thrust surface substantially.
Heard from my friend that had the same trouble with a Suberban and had the restrictor mod. done . He said his trans guy has checked the end play on his crank several times and said it it is still fine.
Hope I have the same luck.

 

Restricted cooler, kinked lines, something is causing the vent side of the converter, the lower cooler line on the trans case to be restricted. Steel braid can delam internally and cause havoc. There is NO other way for the pressure to build enough to balloon or force the converter forward with enough load to take out the thrust. Keep in mind rats don't have a pinned rear main cap, thrust has to be set at assembly, a lot of hobby builders and some 'profesionals' can mess up the procedure and then blame the trans. Ask me how I know it's always the converters fault.

 

Thanks Mike

The trans is in for a full rebuild and mod per the first page, the radiator has been cleaned and redone. I will check out all the cooler lines for kinks and obstructions and I am replacing the external cooler radiator and new flex lines with a new plate type cooler.
My trans guy has this thread a I repeatedly remind him to read it.

Thanks again guys Gary

 

Racers are never wrong, gotta be the trans guys fault!

 

In addition to the above I think I will replace the flex plate with an original replacement. Not sure if it could have anything to do with my problem but it looks new and something that has been done to this setup lately is causing this problem.

 

My trans guy has come up with an 8 bolt 895 pump stater with a relief valve. His opinion is that G.M. eliminated this relief valve as a cost saving and in extreme instances causes this problem. Also my vehicle had a thick racing flex plate installed which will be replaced with a stock one. He is a having a special Allison converter built with pressure relief holes. And I will be installing an 11 X 22 X 1 1/2 in. plate type cooler. Not sure if I got all the facts correct but this guy seems to know his stuff. Hopefully all this will fix my problems.
Gary

 

I have no experience with the relief valve but in my opion the restrictor mod is a proven fix and if the restirctor mod was used the special Allison converter wouldn't have been needed.
And maybe GM stopt using it because it doesn't work?
Might not be a problem but a possible problem i see with this relief valve is it regulates the presure AFTER it went thru the converter.

I would like to know at how much pressure the relief valve opens, cooler line pressure should not be more then 60psi.
Marc.