727 trans slippin and grabbin in reverse

[CrazyPete]

do you know what kind of clutch packs/ clutch band materals are in this "fully race tranny"?  I had a bad experence with hughes bands and clutches when i build my last 727 there only really made to last a season or so then they need replaced.  Their kinda like wet/dry sand paper they grab awsome but fade with time.  Alot of people are using kevlar lined clutches/bands now too they claim they will last as long and handle the abuse but last like OEM.  Anyway good luck trannys can be frustrating but once you get all the bugs worked out there awsome.

[F N Cuda]

Thanks Crazed,
Yeh, I wish I knew more about the guts to this tranny. Could answer alot of questions. I guess I'm stuck with too little info on it.
Think I'll just cruz it around til I can't stand it any more. It works so sweet in the forward gears and I'm just not ready to hand it over for surgery unless someone can convince me it won't cost a full tranny job anyway.
I can't see doin a touch up, it never pays off. So, boogie til it pukes?

[Follicly Challenged]

OK, so no engine braking in first, thats typical of full manual/reverse pattern type stuff. What it means is the rear sprag is the sole "reaction member' for launch, devoid of the low band apply for back-up and engine braking.
But as far as I know, the low band is still required for reverse, as the sole reaction member, without it, NADA, just a bunch of spinning planetaries, or, if the servo/band are intermittent, they spin, then grabs, and try to go the other direction, The "clunking" as it takes up the lash in the geartrain. OUCH ! go easy until you get this fixed !

What I'm guessing, and I stress "guessing", because like I said, "I ain't much of a Trans guy anymore", is that it's still a rear servo problem, that actuates the rear/low band.
As far as I remember, I don't THINK a guy can get it out from underneath, by removing the valve body ?
Check with somebody more current, maybe you can get at it in the vehicle ?

Hope this helps, FC out.

[Fishy68]

The problem could be a reverse servo leakage seal problem. This can be accessed without removing the trans but the valve body will have to be dropped. This is no biggy for any experienced trans. tech but the hard part is the disassembly/re-assemby of the rear servo. They can be done but they aren't real easy for the light hearted. It's best left to the experienced. The best bet is to first run a pressure test which can be done before even dropping the pan. On the back side of the case is a 1/8" pipe plug screwed into the case that goes into the reverse servo passage for test purposes. You can screw a hydraulic test gauge into it and with the car jacked up in the air on jack stands and warmed up start it and and warmed up and the pressure should be approx 105-140 @ 2000 rpm in either manual low or reverse. If this pressure checks out the problem is probably internal gear damage. Hope not, that's never good news.

A manual valve body that does not apply braking in low is not designed for street use and should not be used for street use although many guys have been lucky for yrs. and used them. The trick is to NEVER/EVER downshift into low while moving. This can damage the sprague or make it spin in the case. Many transmissions have blown to pieces doing this. You should always wait until your stopped to downshift to first.

I know you say you'll cruz it till you can't stand it no more but you have to look at it this way. The longer you cruz it the more damage you do. You may even trash the forward gears by sending trash through them. Just something to think about.

Good luck FN Cuda

[F N Cuda]

Thanks guys,
I've got some feelers out in the trans world and I've decided not to roll the dice.
Several of youz guys got me convinced it might be salvageable.
One opinion also suggested the front pump is probably the problem, easy out but tricky back in. Leave it to a pro.
I'm off to the money tree. Where is it again?
 

[tactransman]

If the pump was the problem you would have a problem in forward too. Go after that reverse servo I think she is cracked!!!!

[F N Cuda]

Again, Thanks for ALL of the input, I take all advice seriously!

[Fishy68]

Best of luck FN.