Kick down and change up on A500 42RH

[Headintheclouds]

Having swapped my 727 transmission for a newly rebuilt overdrive A500 I am now happy with gear changes at light throttle opening but at WOT I get upshifts around 3500 to 4000RPM and I can't kick down to second above about 55MPH. I have checked that at WOT the lever on the transmission is very nearly fully rearwards.

Any suggestions?

 

[Desoto291hemi]

Is your transmission an A500
Or a 42RH ?
It makes a difference

Tommy

 

[Headintheclouds]

It is a 42RH. My understanding is that both 42RH and 42RE are A500, therefore my transmission is both A500 and 42RH. Did I get that wrong?

 

[Desoto291hemi]

The A500 is an all electronic shifted trans
The Rh is still hydraulic shifting with a governor valve doing the shifting

 

[Headintheclouds]

Mine is Hydraulic shifting.

 

[Desoto291hemi]

Okay
How do you apply the overdrive and the lockup converter ?

Tommy

 

[Headintheclouds]

Not sure that's relevant to this issue but I use something similar to the PATC kit. Separate pressure switches / vacuum switch / throttle position switch to operate separate relays for LU and overdrive.

 

[Desoto291hemi]

Well

It’s relevant because in your original post you stated A500
The A500 cannot be operated with the PATC system
I was just asking
Sorry for bothering you
Tommy

 

[Headintheclouds]

No worries. Everything I read tells me that A500 is a series that includes 40RH/42RH/40RE/42RE/44RE but I really don't want this thread to go off at that tangent. I really need some help sorting my gear changes.

 

[Desoto291hemi]

Well
If your transmission is what you say it is
It can only be your governor or the valve body

Tommy

 

[Desoto291hemi]

There is a possibility that your throttle cable is out of whack but I really suspect the valve body

Tommy

 

[Headintheclouds]

I originally had Sonnax Lube regulated pressure regulator valve and manual valve fitted. My transmission builder wasn't sure of whether this had anything to do with it and we didn't know the history of the valve body and whether it had been modified so we sent off a spare valve body to be checked and reconditioned with original type valves. It was checked on the rig in the picture and seemed fine. I'm not sure about the governor but the test port is used for the pressure switches for LU and overdrive and these operate at roughly 45 and 50PSI and come on at around 45 to 50MPH so they aren't miles out.

 

[Headintheclouds]

The kick down lever is fully forward at idle and fully to the rear at WOT. As the issues I'm describing are at WOT I think the only relevant point is that the lever is fully towards the rear. at this time.

 

[Desoto291hemi]

Yes
If it’s at full travel it’s not the cable

I’m sorry I don’t have any more help for you
There’s many on here that are very knowledgeable about transmissions
Maybe they will chime in ?
I hope you get it fixed

Tommy

 

[Clelan]

A-500 and 42RH are hydraulic shifted with a solenoid for the overdrive. 42RE requires computer control. Mods to your shift points as described above would be done the same as any hydraulic transmission (A904,A998 & A999). I do not have yhe knowledge to tell you how to make thise shift point changes, but I an curious too.
I just didn't want you to be led astray with the incorrect info about the A-500.

Cley

 

[Desoto291hemi]

The A500 is hydraulic shifted you say ?
My apologies gentleman .

Tommy

 

[Headintheclouds]

According to the Automatic Transmission Service Group ATSG the 42RH is A500 and the 42RE is A500SE

Attached picture also suggests A500 is transmission type with a number of 40, 42 and 44 variants.

 

[Desoto291hemi]

The ATSG should know .
I always thought that the A500 was the last one in the food chain when it went electronic .
Sorry for leading you astray .

My sons 98 Dakota had an A500 and it was all electronic .
I should have read closer on the details I guess .
I didn’t realize that all of those units were under the same umbrella .

Tommy

 

[volaredon]

The A500 is an all electronic shifted trans
The Rh is still hydraulic shifting with a governor valve doing the shifting

The A500 was renamed 42/44RH.
Then they changed into the 42/44RE.
Originally that series was called a500

 

[Frankbassman]

What year 42rh?

Mine is a late '94.

I just went through this. The late hydraulic RH (NOT ELECTRONIC RE!) have an annoying aluminum smaller governor with zero aftermarket possibilities to tune up the shifts.

Not that you would want to pull the OD to get to it anyway. It is a much bigger pain than the 3 speeds.

What to do? You'll have to get real creative with finding springs for both the 1st to 2nd shift valve, and the hard part is the 2nd tp 3rd shift valve.

For the 1-2 shift, A&A sells a kit of two springs.

For the 2-3 shift, you'll have to do some research. I have not found anyone selling a stiffer spring for that shift.

My 42rh has a part throttle kickdown module.

Bonus information: some 42RH transmissions do not like the sonnax manual valve and CREEP IN NEUTRAL. If yours wants to creep forward in neutral, switch back to the original manual valve immediately.

The sonnax pressure reg is fine though.


If anyone has tricks for raising the part throttle sensitivity and the shift points on these units besides blocking the ptk valve and a governor change, let the class know!

-Frank

 

[Headintheclouds]

My 42RH is July 1991. Pleased to report that with the Sonnax valves fitted I wasn't getting any creep. It sounds as though I am best off going back to the other valve body, enjoying the low RPM cruise and part throttle kickdown and forgetting about the early WOT down shifts. Having just had the car dyno tuned I'm hoping for some decent MPG.