TH400 case

tkr

Well-Known Member
Are there any aftermarket cases for the TH400 that are stronger than stock? We have a customer with a motorhome that has snapped the bellhousing on four of them. We've checked all the mounts and the geometry seems to be ok, so I'm assuming that its just a big coach towing a 40 or so foot boat that's the cause.

Matt Nelson
Team Kwik Racing
 

rdc

- users no longer part of the rdc family -
Check to make sure the driveline is balanced.. I would guess you might not fell the vibration in a big motorhome possible. The bell housing shouldn't be seeing torque load..

Tony
<A target="_blank" HREF=http://www.y-not-productions.com>www.y-not-productions.com</A>
 

tkr

Well-Known Member
We've tried that. The last time it happened we put some new u-joints in and had the driveshaft balanced. There is no play in the pinion either. This last time it cracked, he actually heard it snap for the first time. He was pulling into his driveway, which is pretty steep. So I'm thinkin the way the chassis twists while he's turning into the incline combined with the weight of the coach and the boat, and the engine torque twisting in the opposite direction, its just too much for the driveline. And the bellhousing is the weekest link.
This is all just a theory and I'm open to any suggestions....

Matt Nelson
Team Kwik Racing
 

ntsqd

Well-Known Member
I've heard of that sort of thing happening when the rear face of the block isn't square to the crank centerline.
Also, check that the alignment dowel pins are in the right place. It's common enough for those to be off that eccentric pins are available.

TS

"It only seems kinky the first time"
-- Bumpersticker seen in Lost Wages
 

FABRICATOR

Well-Known Member
Is that poor thing behind a stock 454? Have there been other major modifications to the driveline or mounts? Torque from even a healthy 454 should not break a TH400 case. I would suspect binding of some sort on that trans. I don't think anyone makes an aftermarket case for a 400. But they do make a replacement bell housing, originally designed for drag racing. The original is machined off and the new one bolted in its place. It is said to significantly increase the torque capacity of the case. Another thing he might do is use a 4WD case. These are the same as 2WD except for the several threaded bolt bosses around the converter cover. They use a hefty cast aluminum cover that bolts in place with several bolts instead of stamped cover with 4 screws. There are plates that go under the side motor mounts, and bars that go from those plates to the bottom of the bolt on cover. These were on most heavier duty 4WD trucks and were also used on the TH350 as well. The cover costs about the same from the dealer as from the junk yard, at about $20. One last option (short of an Allison) is the 4L80E. These have a significantly stronger case and are designed for more GVW.

<font color=orange>The best ideas are the ones that look obvious to the casual observer.</font color=orange>
 

tkr

Well-Known Member
Fabricator -
Yes, its behind a stock 454. That's why I think its gotta be chassis flex that's causing it...or some kind
of misalignment issue. You're the second person to suggest the aluminum cover to me today. So I'll definitely look into that on Monday. I appreciate the advice.

Matt Nelson
Team Kwik Racing
 

Kritter

Krittro Campbell
Check the motor mounts.

Kris
<A target="_blank" HREF=http://www.dmsrace.com>www.dmsrace.com</A>
"Jesus loves you, everybody else thinks you're an A-hole"
 

tkr

Well-Known Member
We replaced both engine mounts and the transmission mount the last time...

Matt Nelson
Team Kwik Racing
 
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