[twobullman]

06 2500, 48RE was rebuilt and upgraded, torque converter, clutches, shift kit and new electrics. This is what I was told was done to it about two years ago. I got stuck on the beach and was pulled out. Now when I put the truck in reverse it will engage, but when I push the gas pedal the engine revs, but the truck doesn't move any faster. Drives great forward. Does anyone have any experience or knowledge on this?

 

[SRLAX86]

I would drop the pan and check the rear servo. See if its cracked or ed in the bore, check the adjustment on the rear band also. Could be a smoked front clutch but if that's bad it should slip in third gear also.

 

[bigtow30t]

If I remember it has an adjustable band for reverse

 

[Klevingston]

Rear/Low band issue. Put in Manual 1st and see if you get same result as Reverse. This is the only 2 times Rear Band is relied upon, and since you have normal driving when placed in "D", most likely culprit. When you pull pan to inspect, also use a flashlight to look at Rear/Low Drum for scarring even if adjustment is tried first.

Sometimes the Rear servo can get sideways in bore (mine did this after install of aftermarket valve body) and as soon as I touched the actuator arm in pan, it popped back. It was time for billet servos.

 

[twobullman]

Manual first drives great. Overdrive works fine too. Haven't noticed any slipping in third either.

 

[NeMachinist]

The clutches in the rear (forward) drum ran out of friction material, now the steels, and the steel core of the friction plates are welded together.
This causes the forward clutch to basically be engaged all the time, not allowing reverse to function.
Been there, done that.


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[NeMachinist]

I'll try to explain a little better.
All your forward gears work because the rear clutch (welded so on all the time now) is used for all forward gears. Manual low, second, reg drive, OD, all of them.
Reverse is achieved when the front (direct) clutch applies and the low/reverse band.
Drive/3rd gear is the application of front and rear clutch.
But what's happening now when you put it in reverse is the front and rear clutch plus the low/reverse band all apply...equals you going nowhere backwards.


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[dixon700]

What could cause it on a trans with only 30 miles on it?

 

[Klevingston]

read my post above. My OEM Rear/Low Servo tweaked sideways and caused Rear/Low Band not to release when went from "D" to R"

You can hose a Rear Band in much less than 30 miles

 

[NeMachinist]

You're just going to hav to tear into it and find out.
Sound like kelv has had a similar problem and what he found was the problem.
My nephew had what I would describe as the same issue and description two months ago after pulling someone out on a mud road.
Thick mud that took lots of go pedal. That trans was put in by a shop and was only a couple years old with maybe 10k.
We found the forward clutches friction-welded together. Replaced them and he is going again with no problem.
If your putting out more torque than the clutch could hold then you could smoke them in seconds.
When you find the problem let us know, so the next guy with same prob has a place to start.


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[NeMachinist]

You could do a test pretty easily to see if the low/rev band is applying.
Put gear shift in manual low, drive to a fairly high rpm, let off the gas and see what happens.
If you coast freely and the rpm quickly drops to idle, then kelv is on the right track and your rear band in not applying.
If you have engine breaking and the trans slows you down, then the rear band is working.



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[cerberusiam]

There are 3 components active in reverse, diorect clutch pack, rear band, and OD direct clutch pack.


If you still have drive and it shifts into it correctly it is not the direct clutch pack.

If you weld the forward clutch pack you will not have reverse at all, you will not have neutral, and it will load the engine in park.

It either the rear band or the OD directs, usually. If you have manual first and you feel no free wheeling when letting off the throttle at speed in manual 1st, OD directs are slipping.

 

[NeMachinist]

There are 3 components active in reverse, diorect clutch pack, rear band, and OD direct clutch pack.





If you still have drive and it shifts into it correctly it is not the direct clutch pack.



If you weld the forward clutch pack you will not have reverse at all, you will not have neutral, and it will load the engine in park.



It either the rear band or the OD directs, usually. If you have manual first and you feel no free wheeling when letting off the throttle at speed in manual 1st, OD directs are slipping.

If the OD directs are slipping so badly that the truck won't move in reverse then how could he hav the forward 1-2-3's working?
Doesn't the OD direct disengage in neutral and park?..I really don't know the answer.
It would be wonderful if the op would do the manual low test so we had some info. 🙏


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[dozer12216]

Yak, Yak, Yak.
Cerberusiam got it right....

My estimate is when stuck in sand you burnt the rear band or od direct clutch from you description..
Either failure gonna require overhaul.
Lesson: Use 4 low on sand if equiped. Don't take 2WD on soft sand.
The engine has enough power at stall to burn trans out in less than a minute of abuse.

 

[NeMachinist]

Yak, Yak, Yak.
Cerberusiam got it right....

My estimate is when stuck in sand you burnt the rear band or od direct clutch from you description..
Either failure gonna require overhaul.
Lesson: Use 4 low on sand if equiped. Don't take 2WD on soft sand.
The engine has enough power at stall to burn trans out in less than a minute of abuse.

I certainly wasn't arguing. I was asking questions that I did not know the answer tothat pertain to the op's prob.
I also would assume cerb has it right, judging from countless hours of reading the forum.
I have worked on a 47re trans first-hand that hand welded forwards and the engine ran free in park and neutral.




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[dozer12216]

No argue. Just the blunt facts. you see.

 

[Klevingston]

The link here is a good read for the 48RE.

Scroll down a few pages and you will also see a Band and Clutch Apply chart.

http://www.brasilautomatico.com.br/downloads/48RE_br56.pdf

 

[cerberusiam]

If the OD directs are slipping so badly that the truck won't move in reverse then how could he hav the forward 1-2-3's working?
Doesn't the OD direct disengage in neutral and park?.

The OD directs are supposed to hold in forward gears also, but, there is a sprag clutch in the OD unit that will hold on forward movement also. You lose the OD directs and sprag engages going forward but releases in reverse so slippage or just burnt out and it doesn't go reverse.

The OD directs only disengage in OD, that is the clutch pack that is applied with the 800 psi spring and is hydraulic release. The sprag clutch allows the OD directs to disengage first then the OD ltuch pack applys to get OD. This was a problem in the 518's and early 618's as the clearance on the OD clutch pack was too tight and would apply the OD clutches while the directs were still engaged. The puny OD clutches never stood a chance when that happened.

He did say, the way I read it, that the truck would move in reverse just not very fast and it would not accelerate. Any time I smoked a rear band, jammed or broke a rear servo, there was NO reverse. That may not hold true if the piston is slightly cracked or hanging at the top of the bore with the band partially applied. A pressur echekc of the rear servo should eliminate the servo being broke or sideways in the bore as the pressure is usually low when that happens.

Any time I have seen a direct clutch pack welded, and I mean well and truly welded to where you had to beat it apart, it moved in neutral from parisitic flow of fluid and loaded the engine in park. However, there are other things that could go wrong or break and it would not move in park either so it is not a hard and fast rule, just a general observation.

 

[NeMachinist]

The OD directs are supposed to hold in forward gears also, but, there is a sprag clutch in the OD unit that will hold on forward movement also. You lose the OD directs and sprag engages going forward but releases in reverse so slippage or just burnt out and it doesn't go reverse.



The OD directs only disengage in OD, that is the clutch pack that is applied with the 800 psi spring and is hydraulic release. The sprag clutch allows the OD directs to disengage first then the OD ltuch pack applys to get OD. This was a problem in the 518's and early 618's as the clearance on the OD clutch pack was too tight and would apply the OD clutches while the directs were still engaged. The puny OD clutches never stood a chance when that happened.



He did say, the way I read it, that the truck would move in reverse just not very fast and it would not accelerate. Any time I smoked a rear band, jammed or broke a rear servo, there was NO reverse. That may not hold true if the piston is slightly cracked or hanging at the top of the bore with the band partially applied. A pressur echekc of the rear servo should eliminate the servo being broke or sideways in the bore as the pressure is usually low when that happens.



Any time I have seen a direct clutch pack welded, and I mean well and truly welded to where you had to beat it apart, it moved in neutral from parisitic flow of fluid and loaded the engine in park. However, there are other things that could go wrong or break and it would not move in park either so it is not a hard and fast rule, just a general observation.

That's good info. Thanks! 👍


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[dixon700]

I think mine is going to be rear band related because engine braking wasn't working great after I lost reverse if I blipped the fuel pedal just right I'd get some braking. I gotta go out today and measure rear servo psi. Then I'll have to go from there.