Engine/Transmission (1994 - 1998) To all you 48RE autos out there

[Bart]

I have an auto, built by one of the two top, builders associated with this site.

My problem is that while pulling in second gear, either loaded or empty, and manually shifting through the gears the darned thing will shift out of second into third even though I've still got the lever in 2nd. When towing heavy this drives my egts up. What's the point of having 3k or 4K gsk when this happens? First and third will hold until heck freezes over and pull to whatever rpm I need and shift at, but not second. Is there something wrong with something????? I just bought a new 39' toy hauler and can see this thing choking just when I need it most.

 

[Tinman]

Does it buck between 2 and 3?



My 01 does this too, both stock and with the DTT. I talked to Bill K. and he said it was a Chrysler design flaw. Something about when in second and the line pressure gets to a certain point it shifts to 3 even though it's in 2nd. Their transmission controlled prevents this when it is on. I haven't experienced this with the 48re. Maybe ATS's controller will help.

 

[Ridesamule]

I have noticed this on occasion also, once this weekend in fact. I was pulling around 23k up a dug way (major turbo bark was the result).

I think I may have figured it out tho, I'm not so sharp any more but sometimes a persons memory can surprise them. Any way I forced myself to look down and observe my gear selector, prior to any other reaction. It was not clearly in 2nd gear but drifting between 2-3. I pulled it down to the stop and it didn't happen again.

I'm hoping this was the problem and plan to check all of the linkage over.

 

[JoshPeters]

The easiest way I can try to help explain this is...

Take an H for example. If you have more pressure on the top side then the H goes down. When the pressure pushes up, it has to be greater than the pressure going down. Depending on the spool valve, there will be a spring to make it an even greater pressure. What ends up happening is when the pressure gets high enough it aborts the shift and forces the shift to 3rd. I will assume it does this because 2nd gear is applied through the front band, and the band strut. As RPM Rises so does the pressures within the transmission. Chryslers Default may be due to the factory weak band strut. If the pressure gets to high it would either bend or flex that band strut causing 2nd gear to slip.

JP

 

[Bart]

I guess my only opinion is to build the engine to the point that it doesn't need 2nd gear. So far my limiting factor has been the egts. After finding 3 intake leaks the truck will bury the 35 psi boost gauge with only 1200-1300*. I'm working on getting a head with o rings, better cam, water/meth injection and the best air filter I can get. That with the rest of the stuff I've put on it already, I should be able to maintain speed and temps up most any hills.

Thanks gentleman

 

[Stefan Kondolay]

This is how Bill explained it to me, any chrysler product 47rh, 47re, 48re, the manual selector has very little control of the shift range, sounds kind of silly doesn't it? Governor Pressure is controlled by vehicle speed, throttle position ( throttle pressure ) .



As soon as the lockup circuit is engaged your governor pressure shoots up with it. You can have 100 psi of governor pressure and only be going 20mph.

Guess what that means , your transmission is going to upshift no matter what range you select. As far as the transmission is concerned you are going 100mph. 1 PSI = 1MPH .

 

[tgrfan2]

That is interesting, Stefan. I have never experienced that with my 95,98, or 06 though. I guess you have to be hammering it to get that response? I just wish my 06 shifted like my 98 DTT!

 

[2broke2smoke]

Does it buck between 2 and 3?



My 01 does this too, both stock and with the DTT. .

mine has always done this too ...



and under light throttle at about 2k rpms ...



usually i'm on some small 1 lane back road ...

 

[zstroken]

Governor pressure does control the shifts when it is in Drive, but the manual shift lever blocks some of the circuits. I have seen a guy pull it down to second and guess what it goes to second, it almost through him forward. Chrysler does have some funny algorithms for the governor pressure though. If I recall correctly in Manual 2nd the fluid can't get to the other side of the 2-3 shift valve, to shift it to 3rd. Maybe your shifter isn't adjusted or the "rooster cone" has been tweaked, allowing it to leak by the manual valve when your in manual second.

 

[Bart]

While towing my 39' toy hauler yesterday, I had some very serious bucking just after the 2/3 up shifts. What I learned was that the torque converter being locked up during the two/three shift was just toooooooo intense. In an attempt to solve this problem I turned the rheostat off. End of problem. Unfortantely it also ended the exhaust brake effectiveness. The unintended up shift also stopped being a problem. I'll be talking to ATS and the transmission shop about that.

Just an update.

 

[Bart]

Originally, my rig had a 3 disc t/c and a manual (rheostat) controller. After finding the bucking solution. I started adding more rheostat back in to the mix and found out that about 3/4 of the way to full scale the trans would shift normally and yet keep the t/c locked up for the ebrake to function. Only change now is that it locks up around 30 instead of the 18 mph that has been the norm for many years. I'm working with ATS to maybe changing to their commander control or pilot (something or other).