Fresh TH400. Launches fine thru 1st, fraction of a second into 2nd motor pulls down noticeably (not a bog) for a fraction of a second then picks up again. Feels like tire rub so I changed to a narrower section slick but it does the same thing except last night it twisted my drive shaft in half and tore up my steel floor real good.
Any ideas?

Does your converter have a sprag ?

No sprag. New converter.

This message has been edited. Last edited by: SS427IMP,

Maybe I'm not thinking about this correctly but how does a trans binding twist the drive shaft? Sounds more like a rear issue.

quote:

Originally posted by RB72Duster:
Maybe I'm not thinking about this correctly but how does a trans binding twist the drive shaft? Sounds more like a rear issue.

I was going to ask the same question

Unless the trans locked-up internally there is no way it can bend the driveshaft going down the track.......

And there had to be skid marks from the rear wheels locking-up, or that driveshaft was on it's way out to begin with.

Drive shaft might be a separate issue although I thought it would go at launch, not 2nd gear.
Rear seems ok, spins freely, no noise.
Shaft splines (internal)are chewed up a little, haven't had time to check tailshaft splines or if trans moves freely in neutral.
Let's forget about drive shaft for now, what would cause motor to pull down in 2nd?

quote:

what would cause motor to pull down in 2nd?

A bind up in the transmission will cause that.

On the power flow, do you know if the low-reverse band is applied in low gear?

I had a 3 speed transmission that had some severe shift overlap, when you put it on jack stands and ran it thru the gears it would STOP during the 1-2 shift. Going down the track it felt like a bog.


Joe

quote:

Originally posted by Trans Lady:

quote:

what would cause motor to pull down in 2nd?

A bind up in the transmission will cause that.

On the power flow, do you know if the low-reverse band is applied in low gear?

Don't know but I'll find out!

I have a TH350 that would throw us curve balls from time to time. We would lose exactly .1 and never feel it do a darn thing!

Could go 10.90 on a few passes, then 11.00, then another 10.90. Chased this a long time. Changed convertors, no change. Rebuilt the engine, changed compression, changed cam, still same thing happened.

Finally did a glide and the car was now perfect.

Trans owed me nothing, LOT'S of passes on it, just find it strange that it could do that yet we never felt a thing. Data logs did show a slower acceleration rate 1st-2nd and 2nd-3rd on the slow passes.

I would have the trans inspected at the very least. With driveshaft breakage, many times there is also damage to the trans.

After closer inspection bell housing is cracked all around and one trans mount ear broke off .
Trans shaft splines look OK though .
Oh, and motor not frozen .

quote:

Originally posted by SS427IMP:
After closer inspection bell housing is cracked all around and one trans mount ear broke off .
Trans shaft splines look OK though .
Oh, and motor not frozen .

Sorry to hear that. Years ago a u-joint cap came off in the burnout box then all he!! broke loose! Got a new driveshaft made, got a new tailshaft for the Dedenbear case. Was changing it at the track, went to tighten the bolts on the new tailshaft and thought the trans was spinning. It was hot and humid, thought I was dizzy......... I try again, and the case is moving!

I get out of under the car, look down at the trans, and see a crack completely around the entire trans!

Just had that case recertified too. It was DESTROYED!

That was over a $3000 burnout!