Th400 tailshaft roller bearing

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Th400 tailshaft roller bearing

Post by jacksoni » Tue Sep 15, 2009 1:55 pm

Th400's are known to push out the tailshaft/slip yoke bushing in high speed applications. I have a Richmond 5 speed that uses the same bushing/seal/yoke and is doing the same thing. TCI makes a tailshaft with roller bearing but don't sell the bearing nor could tell me what it is/where comes from. Can anyone point me to a bearing source/kit/trans modifier who does this sort of modification?

Thanks,
Jack

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Post by BLACK BART » Tue Sep 15, 2009 7:16 pm

Hi Jack, try contacting Jerico, Liberty, Lenco, Jeffco?, or any other aftermarket transmission manufacturer. I imagine they would be your best bet.

If you have a way to do the machine work or have someone who can, I know the TH400s used in the larger UPS type delivery vehicles had a roller bearing in the tail housing. You could use one as a blueprint to machine your tail housing and get a part number from the bearing if you could find one.

You will also need a hardened slip yoke if you use a roller bearing. These can be purchased from aftermarket sources for $100.00-$150.00 if I remember correctly.

Good luck, CJ
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Post by jacksoni » Wed Sep 16, 2009 9:05 am

Thanks, CJ. Just looking at the websites, some of the high end transmissions seem to not use a slip yoke, but I will check with them for ideas. The Truck th400's have a fixed yoke but can be converted to a slip yoke per some other info I have seen. The bearing has not been mentioned in what I have seen but will check into that as would be a good source. Thanks for the idea.

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Post by cjperformance » Sun Sep 20, 2009 9:46 pm

The bush moves due to the ammount of load induced expansion of the slip yoke. Going to a roller bearing does not fix this, all you get is higher point pressure which damages the slip yoke and rollers.
A bush has way more surface area than a set of rollers and if lubed properly and has a strong enough yoke that is not prone to expansion from load will live without problem.
Look at the splines on the output shaft, they are angled so when they transmit high ammounts of tq load they cause the slip yoke to expand, this is your problem and its not just in T400's.
Look at a heavy duty/industrial spline, it has square drive edges so that there is little or no load induced expansion of the yoke.
You need a good quality, high strength yoke and quality bush fitted with the right press fit and proper lubrication. The tailshaft alignment and uni joint clearance are also important.

A hardened yoke, depending on the application can be prone to cracking under severe use ie, trans brake, s/charging, n2o, big slicks, race clutch/launch etc. Then more damage can occur.

The correct yoke and bush for the tq app is the easiest.
Or, roller bearing and fixed yoke that is designed for roller bearing use as in high end trans's. To go this way you may need to change your tailshaft arrangement aswell.

There is really nothing at all wrong with a bushed slip yoke, so long as it is up to the task. Many times I have seen a slip yoke converted to run a roller bearing only to end up causing more problems and broken extension housings, cracked yokes, front uni failures and short roller life span. Not to mention the time and money that go's into it just to end up converting back to a good old Heavy duty slip yoke and bush.

Sometimes its better to strengthen the wheel rather than reinvent it.
Craig.

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Post by jacksoni » Mon Sep 21, 2009 4:41 pm

Thanks for the thoughts, Craig. My yoke is a good one I think though don't know the mfg. got it through Richmond. My engine makes 130ft lbs torque on good day. Skinnny tires on salt. No high loading. That yoke is thick and though I understand what you are saying aobut wedging of the splines and expansion, so I'd be skeptical but certainly bow to superior knowledge. I have found appropriate bearings but feel machining will make the housing too thin for safety ( thus the aftermarket housings). Has been suggested locktite the bushing in. Richmond also suggested plumb some sort of pump to move lube to the bushing- pain the the a** but could be done. Friend has suggested, on reference from a trans builder ex nascar I think, to put a grease fitting to the bushing and give it a squirt time to time ( for me before a run). I have lost a driveshaft at speed- only 130mph at Bonneville before. Broke the crap out of pretty much every part of the drivetrain, back of engine and bottom of the car. Not wishing to do it again by having bearing fail/transmission fail, thus my quest for better than the way it is now.
Again, appreciate your thoughts

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Post by BLACK BART » Mon Sep 21, 2009 5:37 pm

Jack, I just re-read my earlier post and realized that I forgot to mention anything about balance. A poorly balanced drive line, when its at speed, will eat a bushing real fast.

Another thought is that maybe you need to get a drive line that is better suited to what you are doing. A larger diameter/lighter tube will not want to act like a jump rope as easily as a smaller diameter/heavier one. You may need to go with a lighter drive line that's a bit larger in diameter so it's not fussy with the balance while at speed.

Try to find a shop that can balance your drive line at or near the same speed you will be turning it in the car. I know Mark Williams can do this if you can't find anyone else.

Good luck, CJ
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Post by jacksoni » Mon Sep 21, 2009 5:49 pm

Thanks, CJ. Getting the driveshaft balance checked is on my (getting longer) list! My current driveshaft hoop doesn't have a lot of clearance for a larger tube but that is a good suggestion.

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Post by MadBill » Sat Sep 26, 2009 8:39 pm

Further to Black Bart's driveshaft comments, verifying that yours does not exceed its critical speed would be prudent. Wallace racing (well known to us SpeedTalkers) has the scoop: http://www.wallaceracing.com/driveshaftspeed.htm

Also (in keeping with my motto below) why not just find a way to lock the bushing in place? I suspect the issue is differential thermal expansion reducing the press fit. When we encountered this problem on a G-Force road race 5 speed, we built a little retaining collar with 3 set screws and have had no issues since. Probably Loctite Bearing Mount would have worked just as well...
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Post by fastvette » Sat Sep 26, 2009 9:15 pm

I had a bushing in a power glide that kept coming out, and finaly broke the tail housing. All because of drive shaft balance. Never felt any vibration though.

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Post by jacksoni » Tue Sep 29, 2009 10:31 am

MadBill wrote:Further to Black Bart's driveshaft comments, verifying that yours does not exceed its critical speed would be prudent. Wallace racing (well known to us SpeedTalkers) has the scoop: http://www.wallaceracing.com/driveshaftspeed.htm

Also (in keeping with my motto below) why not just find a way to lock the bushing in place? I suspect the issue is differential thermal expansion reducing the press fit. When we encountered this problem on a G-Force road race 5 speed, we built a little retaining collar with 3 set screws and have had no issues since. Probably Loctite Bearing Mount would have worked just as well...
As the bushing is now back in place and getting it out might require disassembly, may go the retainer route. Couple small screws with the position and head sized correctly should work as a retainer I think.

As far as the shaft is concerned, not sure how to come up with all the things the Wallace formula needs ( what is the Modulus for what I have, for instance) but will get it checked for straight and balance.

But if is a heat/lubrication issue seems to be happening pretty fast. I can see a road racer getting in trouble but wonder do I really heat the lube much at all in a 90 second run. Is the bushing getting proper lube ( thus the recommendation from Richmond to rig a pump). Could I over fill the trans a little to try to get more lube to the back?

Thanks for all the suggestions everyone.

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Post by MadBill » Tue Sep 29, 2009 10:58 am

For steel, the value is ~ 30,000,000. For others Google is your friend. The Wallace spreadsheet lists common DS materials i.e. Metal Matrix Composite, 6061 alloy aluminum, 1053 grade steel, but for some reason clicking on a choice does not seem to automatically call up the relevant modulus..
As far as lube, maybe a smear of grease before a run would be cheap insurance. Most motorsport involves high g forces, which will slosh lube onto the bushing, but I've heard of them seizing during repeated chassis dyno tests, which would not be dissimilar to the long slow accels of the Great White Dyno...
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Post by jacksoni » Tue Sep 29, 2009 1:17 pm

"Great White Dyno..."

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Post by MadBill » Tue Sep 29, 2009 5:11 pm

Closest I've been is the tee shirt my kid sent me after his VW van blew the engine near Wendover in 2000 when he was migrating to California. :(
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Post by BrazilianZ28Camaro » Sun Nov 08, 2009 8:19 am

Have you checked the driveshaft alignment angle in ralation to the trans /rear axle ?

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Re: Th400 tailshaft roller bearing

Post by jacksoni » Sat Sep 01, 2012 12:48 pm

I'd like to update this thread with recent events. After the 2009 outing went to a different car for a while, different trans. In 2011 built a new car, still for Bonneville, with the same Richmond 5 speed trans that was the focus of this in the first place. New custom made drive shaft, balanced, carefull shaft alignment with IRS rear (is in a Nissan 240sx changed from the Firebird before>) At the 2011 meet again the tailshaft bearing coming out along with the seal. Subsequently, a synchronizer part broke and, desperate and unable to find a trans locally, we got a NEW trans, replaced it at the track (slip yoke well lubed) and made 1 pass. (2-3mile tow to the start line, one 4 mile run) and the bearing half out, the seal out. We considered that the bellhousing might be out of alignment so this year with a new bellhousing, carefully aligned to less than .005" runout any direction. Made 2 runs, bearing and seal out. We removed the tailshaft housing, clearanced the bearing for extra lube, put it in with red locktight and fashioned a retainer for the seal. Lot of lube on the slip yoke. It is out again after several runs- not sure how many this time as we were focusing on other things. May have wrecked the tailshaft housing- to be determined.
Prior suggestions were that the slip yoke was enlarging with torque and seizing the bearing. Mostly with engine making only maybe 150lbsft torque, I can't believe it. There is NO lube source to this bearing other than a tiny amout that might creep down the output shaft. I think the bearing/yoke get hot from no lube after a while, enlarge and seize, out it comes.
Richmond previously suggested putting a lube pump on it and I think that is where I am going to go, unless someone has a better idea. Any thoughts about what sort of pump and where to source it? I can plumb and wire it ok.
Again, thanks for any thoughts,

Jack

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