Hello everyone, new guy dealing with repeated reverse band failures. The trans is a 47RE, but lets ignore the OD and TC Lockup and stick to the main section of the trans, anyway here we go:

So I had the transmission rebuilt Fall of 2016. I had more money than time back then. Full Manual VB with LBA. No issues for 5,000 miles, then no reverse, no 1st gear engine braking, and no 3rd gear. This was the 1st failure. Nothing goofy inside but a fried rear band. Reverse servo was jammed hard in the activated (towards VB) position. This was an upgraded billet servo no less. It was stuck so hard (somewhat sideways) that I had to hit it with a hammer to get off the band apply arm.

Rebuilt the transmission myself. Drove around for 2 weeks, then bam no reverse in the driveway. Diagnosis? Yup Rear servo stuck and fried reverse band.

Rebuilt it again, this time used a whole different transmission case. I thought maybe the servo bore was out of whack causing the stuck servo (it looked fine though). Also replaced the billet rear servo with Sonax billet one that had more rounded edges. A couple more weeks pass, and bam. Here I sit with another reverse/low band failure.

This rebuild I will be replacing the VB. I am getting pretty good at trans R&R at this point but a little sick of this low band failing.

Any thoughts guys? Why the repeated failures with 2 different types of servos and 2 different cases even. This is a double wrap rear band BTW.

Welcome here. sounds like a very interesting whodunit. Kunkel & the tranny guys will tighten you up.

I'm thinking you have excessive pressure in that servo. I would put a gauge on it and see what it is. Also the adjustment could also be critical here. Too much travel of the servo and it has room to cock in the bore.

Is the servo solid or does it still have a spring on the rod to cushion the engagement?

I will check the pressure today.


The servo still has spring on the piston rod.

For the adjustment, when building the trans I take it to 150 in/lbs, back out completely, then 150 again, then back out again, then 72 in/lbs and 2 turns out,

Had one years ago in a 727, the rear band strut linkage had been installed upside down. Something to check

I wish it could be a jacked-up linkage. My double wrap transmission has no strut linkage. It has a pin that holds one side of the band, and the apply lever acts directly on the other side.

The one thing I am wondering is you said the first time it happened you also had no third gear ? The rear band fried will not effect third gear. Third is the front and rear clutches in the main trans unit. Course power also goes through the O/D direct clutches in first through third. So I was curious about that as you said you found no other problems in it ? Ron

That could be your problem, the 47RE calls for 3 turns out.

http://dodgeram.org/tech/transmission/automatic/AT_band_adj.htm

Oops, yeah on the 1st attempt the front or rear clutch pack (I forget now which one it was) had a mild amount of wear on the clutches. Nothing extraordinary, no warped or blued steels, just faintly brown discolored red clutches. The rear band was gone and drum badly scored. The shop that rebuilt the trans said this was the first time they had ever done a Full Manual VB as well as trying to sell me a Dayco Converter for $1,100. So maybe they screwed something up, but it functioned just fine for 5,000 or so miles.

I also forgot that on rebuild 2 of 3 (my first rebuild after the shop's rebuild) I had the the transmission go into OD and Lock the TC. I have simple On/Off ground switches for both, and when slowing for traffic I noticed the truck trying to stall despite TCC switch being off. I could only get either OD or TC to go off by shifting into 2nd. Then upon return to 3rd, it would instantly go back into OD & Locked. The next day after the OD & TCC shenanigans, no reverse

On my 2nd rebuild (the one that just failed), I also started experiencing OD/TC nonsense. Sometimes it would go to 3rd then instant OD & TCC locked, sometimes 3rd then instant OD without TCC lock, sometimes no OD or TCC. I replaced both solenoids, and after a day or two it would go back to the same. It would even activate OD and Lock Up with the trans harness not connected. When I replaced the solenoids I made sure the lower valvebody valves of OD & TC were free moving.

As for the pressure test, I am getting 250-300psi (not fluctuating just best guess based on 200 psi gauge pegged) for reverse line pressure. The pressure goes to 0 when in Park. The servo is stuck again in the activated position.

Thank you so much for the help guys. I know it's hard to diagnose another's problems over the interweb.

I am at home and can't look it up, but your pressure sounds high. With excessively high pressure, the PR valve is jammed closed and the converter will not fill properly, which is release oil, which could be the cause of the TCC staying on and killing the engine, and maxing the governor pressure to cause it to go into 3rd quickly.
I would double check the pressure issue first and also make sure that you are not cross leaking into the rear servo while driving hot. Keep your gauge on the rear servo, you should have zero pressure there unless in Man 1 or reverse.

Pressures could be high, but I thought reverse pressures were supposed to be 230-280. Now, I have not gotten around to measuring mainline pressures, but a fair number of people run 180-210 psi (in the diesel world anyway). A few have issues over 200 psi, but none have reported reverse issues. Still a possibility though.

No pressures in reverse in any gear but reverse/man low. Would a cross leak still be possible?

The TCC as well as the OD has been acting normally for a few days. When it would act up, it would ALWAYS unlock in 2nd. It only stalled a few times I forgot to downshift from 3rd (which was OD & Locked).

No issues with 3rd gear applying quickly as it's a Full Manual, trans can't shift by itself. Never any harsh shifts or slippage (other than reverse a day or so ago). Trans temps (measured in pan) have always been 120-140 while the weather was in the 80's.

The book says 260 psi in Reverse but it can go higher with cold fluid.

My 250-300 was based on cold fluid. Even if the pressure was something absurd like 400psi, shouldn't the servo release with the pressure drop to 0?

So far the possibilities seem to be:

1) Too high pressure
-Argument against this that others have run higher pressure without servo issues. Why am I the only one to be experiencing this issue?

2) Mystery VB issues
-Funky OD/TCC stuff seem for this.
-Pressure return to 0 out of Reverse is against this, but who knows what it could have been when it failed initially.

I can rebuild this thing again by the weekend, but without knowing why it failed (I thought it was the servo design, then a case fault, now?) I'm very hesitant and on the fence in terms another rebuild and a manual ZF6 swap from a Ford.

I have seen cases that are deformed in the accumulator area that allow accumulator pressure to cross over and apply the rear servo but you state that you changed the case. The same could occur with the VB...check both the case and VB surfaces for flatness.

I dont know what vehicle your running the trans in, and im not a transmission expert by no means but i rebuilt my 48re in my diesel and read alot of truck forums and have heard alot of rear band failures and stuck servos, and almost all of them were transmission had manual valve body with some sort of lockup problem, or bands not adjusted correctly.

Let's get all the info out at once ok?

The additional information you have now provided would have been nice to start with. When diagnosing anything you have to consider the big picture and take into account everything even if it seems unrelated.

So what vehicle is this in, what engine, stock PCM, wiring or how did you wire it, where did you ground it, did you use relays, whose valve body and whose converter and anything else that may seem to be off whether you think it's related or not.

Yup, swapped cases. This time I will be swapping the VB and checking the VB to case areas for flatness.


I'm wondering if this is not a reverse issues but a 1st gear issue...

When the trans was rebuilt by the shop, I did not often use 1st gear as the trans was pretty much rebuilt and I headed off on a cross country move, mostly staying in 3rd or OD. When i arrived at my destination I did a lot of in town driving using 1st. So maybe it lasted the 5,000 or so miles initially and quickly failing due to use of 1st gear.

My Manual VB has a low band apply, I am wondering if the band could be staying applied in 2nd and beyond, what would that feel like? There's no jerking, bucking, or flaring. If anything the trans was smoother than stock on the 1st-2nd gear change.

crlush, Interesting about the stuck servos & band failures. This is a 47RE in a '02 Dodge 2500 CTD. Do you have anymore info? Never seen a thread on it.

Here's some more info:

Engine: 1990's 5.9 P7100 Cummins from Bluebird Schoolbus in a Meritor (Rockwell Toploaders) Axle'd '02 Dodge 2500.

PCM is of no consequence as the trans is only wired to neutral start, reverse lights, and ground switches for OD & TCC. Simple switch, no relay used.

VB is stock Chrysler with unknown brand full manual conversion done by rebuild shop. My wild guess is that it was a Transgo kit as the Fairbanks kit I used years ago did not have a restricter for the front band.

Torque Converter is a Diesel Performance Single Disk, based on it never having issues in any other gear than 3rd/OD I do not think it is an issue and is only acting up due to VB.
No other issues beyond the ones already discussed.

VB and Case were checked for straightness with a machinist's level, no issues.

The servo was also not stuck when I took the trans apart a few days ago. Everything checked out via airchecks on the bench before disassembly (as in bands applying,etc). Rear band applied fine, just bare metal with a badly scored drum. I think something was keep the lowband applied in other gears beside 1st & Reverse, however there were never any heat issues.

If you google 47re manual valve body stuck servo a few come up. Not sure why but have read a few threds on stuck servos and worn reverse bands with manual valve body.

So the trans is rebuilt, still have to install the VB, undecided if the VB is at fault because...

While installing the rear band, when going to 72 inch/lbs and then back off 2 turns as the books say, I noticed that the drum could not be rotated by hand. I mean that thing was firmly gripped. I took the adjuster out 3 turns (3 turns total not an additional 3 turns) and the drum moves again.

Maybe I was just adjusting the band too tight?