2 to 1 downshift - JeepForum.com
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post #1 of 20 Old 07-27-2021, 07:26 PM Thread Starter
rfesu
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2 to 1 downshift

small problem with my 42re

it shifts almost perfectly, doesn't slip, and has never given me any real trouble, but one thing it doesn't do is a 2-1 downshift.

if i'm rolling at low rpm in 2nd and come up to a steep ascent, i can totally floor it, and it lugs badly until it comes up to RPM.

there's no codes, fluid level is good, the and cable is adjusted properly.

any ideas what the problem would be or what to look at? or is that normal behavior somehow?

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post #2 of 20 Old 07-28-2021, 12:13 AM
jtec
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some thoughts- some far fetched but before we do trans work.that.

TV cable - but you mentioned its OK.
You are using a SCANNER - some trans codes do not report with key on off trick.
Trans fluid, you have done the filter, and fresh ATF+4. NOT universial or 1 type fits all.
TPS, they can be problematic. ALSO is your AIRBAG light on?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 20 Old 07-28-2021, 02:11 AM
Delta0
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Quote:
Originally Posted by rfesu View Post
small problem with my 42re

it shifts almost perfectly, doesn't slip, and has never given me any real trouble, but one thing it doesn't do is a 2-1 downshift.

if i'm rolling at low rpm in 2nd and come up to a steep ascent, i can totally floor it, and it lugs badly until it comes up to RPM.

there's no codes, fluid level is good, the and cable is adjusted properly.

any ideas what the problem would be or what to look at? or is that normal behavior somehow?
What happens when you open the throttle wide in a slow and measured way?
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post #4 of 20 Old 07-28-2021, 04:49 AM
mak_v8
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Quote:
Originally Posted by jtec View Post
...ALSO is your AIRBAG light on?
Hi @jtec h,
sorry, just to understand: which is the relationship between Transmission behaviour and AIRBAG Light on?
Thanks

Grand Cherokee WJ 4.7 V8 HO. m.y. 2002
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post #5 of 20 Old 07-28-2021, 05:45 AM Thread Starter
rfesu
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Quote:
Originally Posted by jtec View Post
some thoughts- some far fetched but before we do trans work.that.

TV cable - but you mentioned its OK.
You are using a SCANNER - some trans codes do not report with key on off trick.
Trans fluid, you have done the filter, and fresh ATF+4. NOT universial or 1 type fits all.
TPS, they can be problematic. ALSO is your AIRBAG light on?
i'm 100% sure of the cable adjustment, and except for this one problem, it shifts up and down perfectly fine.
keep in mind it's never failed to do a 3-2 shift which you'd figure would also be affected by any of those things, but not sure the whole story on how this transmission is controlled.

i am using the key on key off trick as my scanner was stolen, but when i did have a scanner i had graphed the TPS and it was good.

Quote:
Originally Posted by Delta0 View Post
What happens when you open the throttle wide in a slow and measured way?
same difference.

there's one hill near my house that is a good example, and how i noticed the problem. it's after a sharp corner that requires slowing right down to a roll, so by the time you go to climb it, you're rolling well below 2000 rpm in second.

it really struggles to get up that hill, and i can run the throttle up and down as much as i want and barely get it moving, but if i manually shift down to 1st at that time, or if i nearly stop so it shifts to 1st on its own, it's good.
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post #6 of 20 Old 07-28-2021, 06:36 AM
jay-h
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Quote:
Originally Posted by rfesu View Post
i'm 100% sure of the cable adjustment, and except for this one problem, it shifts up and down perfectly fine.
keep in mind it's never failed to do a 3-2 shift which you'd figure would also be affected by any of those things, but not sure the whole story on how this transmission is controlled.
...
The 42RE is really based on the old 42RH, which is in turn based on the original 3 speed Torqueflite. In the original system, the 3-2 and 3-1 were two separate hydralic functions (there was no 3-2 in the earliest versions).

Does the 3-1 and 4-1 kickdown work?

Even though there is some electronics, it is still primarily a hydraulic controlled transmission. The kickdown are controlled by governors and hydraulic pressure. The computer has little knowledge about the internal working so there won't be much to go on from codes.

Try playing with the cable a bit, but if this is all that is happening, I'd leave it alone. You could also do a band adjustment, but if it's just a governor issue, I'd kind of leave it alone. Everything else is working, could go on for years without issue.


The link below has some tech info:
http://shop.ukrtrans.biz/wp-content/...alogs/42RE.pdf

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post #7 of 20 Old 07-28-2021, 07:22 AM Thread Starter
rfesu
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oh man i really needed that manual, thanks.

i guess 3-1 probably does work, now that you mention it.

if there's a good chance it's just a governor solenoid or sensor i'd probably just change it myself

one other thing about this transmission that i had just remembered is that this transmission apparently sat outside with no fluid in it for almost a decade. i guess it's a miracle it works at all.
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post #8 of 20 Old 07-28-2021, 07:28 AM Thread Starter
rfesu
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oh man it's frustrating that there's a massive diagnostic/troubleshooting section that will solve any problem EXCEPT the 2-1 shift.
it's not even mentioned.

it does have 'adjust the band' as part of almost every single troubleshooting step, so i guess i'll do that and see if it makes a difference.
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post #9 of 20 Old 07-28-2021, 07:32 AM Thread Starter
rfesu
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general downshift troubleshooting though:

- incorrect tv cable adjustment (ok)
- gear shift linkage adjustment (ok)
- front band out of adjustment **
- hyd. pressure too high
- front servo malfunction
- clutch/servo malfunction
- governer fault
- tps fault (ok)

i can probably check all of the remaining items pretty easily
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post #10 of 20 Old 07-28-2021, 07:38 AM
Delta0
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Quote:
Originally Posted by rfesu View Post
i'm 100% sure of the cable adjustment, and except for this one problem, it shifts up and down perfectly fine.
keep in mind it's never failed to do a 3-2 shift which you'd figure would also be affected by any of those things, but not sure the whole story on how this transmission is controlled.

i am using the key on key off trick as my scanner was stolen, but when i did have a scanner i had graphed the TPS and it was good.



same difference.

there's one hill near my house that is a good example, and how i noticed the problem. it's after a sharp corner that requires slowing right down to a roll, so by the time you go to climb it, you're rolling well below 2000 rpm in second.

it really struggles to get up that hill, and i can run the throttle up and down as much as i want and barely get it moving, but if i manually shift down to 1st at that time, or if i nearly stop so it shifts to 1st on its own, it's good.
If you set a vintage motor bike up correctly, you can kill the engine simply by just opening the throttle quickly from low revs.

I wondered if you were killing your engine when you floored the throttle at low revs.
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post #11 of 20 Old 07-28-2021, 09:31 AM
jtec
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mak_v8 - I did say far fetched, SO the reason for AIRBAG question.
Above post #9 note that governor pressure/fault and TPS is on quick list.

There is a known issue where AIRBAG light being on as a result of clockspring issue will skew the TPS readings. Again why I asked that a SCANNER is used - just throwing it out, an easy check, And easy things first.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #12 of 20 Old 07-28-2021, 02:23 PM
LDWJ
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I would bet you need to replace your governor pressure sensor and solenoid in the transmission. Do the 3-4 accumulator spring while you are in there. Adjust the bands amd put in a new mopar gasket...all the others leak. It will take about an hour to do it all. Change filter and fluid while you are in there. I also always change the pan to one with a dran plug for about $25. Total for parts is around $200. I have had to do it on 3 WJ Laredo now. Pay attention to when you take off from a stop sign. Your first shift is often fin from startup, but then after that it's always stuck in 2nd gear. It will feel sluggish. Count your shifts. You should feel three shifts and then torque convertor lockup amd RPM drop when up to speed. If only 2 shifts, that's most likely the problem. Very common amd simple fix.
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post #13 of 20 Old 07-28-2021, 10:18 PM Thread Starter
rfesu
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Quote:
Originally Posted by LDWJ View Post
Count your shifts. You should feel three shifts and then torque convertor lockup amd RPM drop when up to speed. If only 2 shifts, that's most likely the problem.
it does shift through all gears fine, except it doesn't kick down from 2nd to 1st, that's the only malfunction. so could it still be the gov solenoid? it seems like all shifts would be affected
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post #14 of 20 Old 07-29-2021, 12:19 AM
Delta0
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Originally Posted by rfesu View Post
it does shift through all gears fine, except it doesn't kick down from 2nd to 1st, that's the only malfunction. so could it still be the gov solenoid? it seems like all shifts would be affected
.
If you pull the gear lever back before you put the pedal to the metal does your engine bog down?

If so, it look like you may have an engine / engine ancillaries problem.
If not, you have a very cost & labour effective solution.
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post #15 of 20 Old 07-29-2021, 09:23 AM
LDWJ
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What you are describing is exactly what I've experienced with the governor solenoid several times. I'm pretty confident that is the problem.
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