Another transmission question
07-24-2016, 08:48 AM
#1
Rennlist Member
Thread Starter
Another transmission question
Hi All,
Looking for a bit of expert advice, my '86 ROW S2 Auto 4 speed has, since I got it in January, had an upshift problem from 2 to 3 on part throttle. It initially 1/2 engages and then grabs about a second later. The fact that it grabs and is good once in 3rd would suggest friction surfaces are good and it's an issues in the valve body?
All other gear changes are perfect, it always starts in 1st so that includes 1-2, and kickdown is spot on as well as all downshifts. At WOT the 2-3 shift seems to be fine.
Here's what I've done so far:
1) Checked fluid level as per WSM (installed a temporary camera and LED light so I can watch the level)
2) Drained transmission and TC, installed new filter/gasket and re-filled. Old fluid was good and no burning smell or chunks in the tray but the PO may have changed it just before I got the car
3) Yesterday I installed a new K1 spring kit, drove for a few miles but it seemed to be exactly the same.
My idea is to do the next steps in order of cost:
1) Drive for a while longer and see if the K1 frees up something, I've seen other posts here and on the MB forum that there is sometimes a slow improvement
2) Put some additive in the fluid that might clean sticky valve parts and thicken the fluid a bit
3) Replace the valve body
4) Bring it to a specialist
As I said all other shifts are fine so I haven't touched/tested the modulator or bowden cable as I didn't want to make things worse. The car is driveable I just want to fix this before it does more damage.
Does anyone have a better plan or confirm I'm doing the right/sensible things.
Thanks,
Gary
Looking for a bit of expert advice, my '86 ROW S2 Auto 4 speed has, since I got it in January, had an upshift problem from 2 to 3 on part throttle. It initially 1/2 engages and then grabs about a second later. The fact that it grabs and is good once in 3rd would suggest friction surfaces are good and it's an issues in the valve body?
All other gear changes are perfect, it always starts in 1st so that includes 1-2, and kickdown is spot on as well as all downshifts. At WOT the 2-3 shift seems to be fine.
Here's what I've done so far:
1) Checked fluid level as per WSM (installed a temporary camera and LED light so I can watch the level)
2) Drained transmission and TC, installed new filter/gasket and re-filled. Old fluid was good and no burning smell or chunks in the tray but the PO may have changed it just before I got the car
3) Yesterday I installed a new K1 spring kit, drove for a few miles but it seemed to be exactly the same.
My idea is to do the next steps in order of cost:
1) Drive for a while longer and see if the K1 frees up something, I've seen other posts here and on the MB forum that there is sometimes a slow improvement
2) Put some additive in the fluid that might clean sticky valve parts and thicken the fluid a bit
3) Replace the valve body
4) Bring it to a specialist
As I said all other shifts are fine so I haven't touched/tested the modulator or bowden cable as I didn't want to make things worse. The car is driveable I just want to fix this before it does more damage.
Does anyone have a better plan or confirm I'm doing the right/sensible things.
Thanks,
Gary
Last edited by gazfish; 07-24-2016 at 12:47 PM.
07-24-2016, 09:36 PM
#2
Rennlist
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Hi All,
Looking for a bit of expert advice, my '86 ROW S2 Auto 4 speed has, since I got it in January, had an upshift problem from 2 to 3 on part throttle. It initially 1/2 engages and then grabs about a second later. The fact that it grabs and is good once in 3rd would suggest friction surfaces are good and it's an issues in the valve body?
All other gear changes are perfect, it always starts in 1st so that includes 1-2, and kickdown is spot on as well as all downshifts. At WOT the 2-3 shift seems to be fine.
Here's what I've done so far:
1) Checked fluid level as per WSM (installed a temporary camera and LED light so I can watch the level)
2) Drained transmission and TC, installed new filter/gasket and re-filled. Old fluid was good and no burning smell or chunks in the tray but the PO may have changed it just before I got the car
3) Yesterday I installed a new K1 spring kit, drove for a few miles but it seemed to be exactly the same.
My idea is to do the next steps in order of cost:
1) Drive for a while longer and see if the K1 frees up something, I've seen other posts here and on the MB forum that there is sometimes a slow improvement
2) Put some additive in the fluid that might clean sticky valve parts and thicken the fluid a bit
3) Replace the valve body
4) Bring it to a specialist
As I said all other shifts are fine so I haven't touched/tested the modulator or bowden cable as I didn't want to make things worse. The car is driveable I just want to fix this before it does more damage.
Does anyone have a better plan or confirm I'm doing the right/sensible things.
Thanks,
Gary
Looking for a bit of expert advice, my '86 ROW S2 Auto 4 speed has, since I got it in January, had an upshift problem from 2 to 3 on part throttle. It initially 1/2 engages and then grabs about a second later. The fact that it grabs and is good once in 3rd would suggest friction surfaces are good and it's an issues in the valve body?
All other gear changes are perfect, it always starts in 1st so that includes 1-2, and kickdown is spot on as well as all downshifts. At WOT the 2-3 shift seems to be fine.
Here's what I've done so far:
1) Checked fluid level as per WSM (installed a temporary camera and LED light so I can watch the level)
2) Drained transmission and TC, installed new filter/gasket and re-filled. Old fluid was good and no burning smell or chunks in the tray but the PO may have changed it just before I got the car
3) Yesterday I installed a new K1 spring kit, drove for a few miles but it seemed to be exactly the same.
My idea is to do the next steps in order of cost:
1) Drive for a while longer and see if the K1 frees up something, I've seen other posts here and on the MB forum that there is sometimes a slow improvement
2) Put some additive in the fluid that might clean sticky valve parts and thicken the fluid a bit
3) Replace the valve body
4) Bring it to a specialist
As I said all other shifts are fine so I haven't touched/tested the modulator or bowden cable as I didn't want to make things worse. The car is driveable I just want to fix this before it does more damage.
Does anyone have a better plan or confirm I'm doing the right/sensible things.
Thanks,
Gary
I would have started there.
2. You have vacuum at the modulator?
3. Does the modulator hold vacuum? (The rubber cap cracks and can leak so badly, the modulator will almost not function.)
I've certainly got some other things you can try, but you really need to start with the basics.
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
07-25-2016, 04:49 AM
#3
Rennlist Member
Thread Starter
Thanks Greg, I did put my vacuum tester on the pipe under the hood and it held vacuum but that could just mean there is a blockage so I'll take a look at the transmission end. Given that the other shifts have the correct firmness and shift point made me think it was a 2-3 specific component.