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trans will not pull in any gear
Sent to Car Experts August 05 11:16 PM

I"m a ASE Master tech and now have a challenge brought to me that is rattling my cage. It is 1988 420sel with the 722.3 trans. The problem is that it will not pull in any gear unless the rear wheels are off the ground but another problem, is that when the trans is in reverse the wheels will still turn forward as long as there is no pressure on them the hyd. pressure is good I have high volume coming from the cooling lines. I have build hundreds of trans with out this problem except when there was a torque convert problem i have installed a new converter but still the same problem. The trans was working great one day and them the next morning the car would not move no matter what ( the trans was not rebuilt). I removed the pan and the fluid was in brand new condition with no metal or other objects in the pan. with the converter out you could turn the input shaft and the output shaft would also turn but not a lot of drag on either end of the shafts. I have had this problem before but it was always the converter at fault. please give me some ideals.Bill at XXXXX@XXXXXX.XXX

 

Optional Information:
1988 Mercedes-Benz 420 sel 256 cu

Already Tried:
pressure test, cooling line flow test, removed pan and inspected, replaced torq converter

Customer (name blocked for privacy)
Status:  Closed   Value: $20
Answer
August 6 6:14 AM (6 hours and 58 minutes and 16 seconds later)
         
ACCEPTEDCheck Mark

http://www.transtec.com/tech_insert/94642.pdf

You might have a worn plastic/rubber check ball, or more than one, causing a misrouting of fluid thru the valve body.

Did you run a line pressure test? Flow doesn't necessarily mean ample pump pressure.

http://66.102.7.104/search?q=cache:wpBnsBy_lQMJ:www.autocd.ru/Atsg2005Bulletin.pdf+mercedes+722.3&hl=en&gl=us&ct=clnk&cd=29#41



Edited by Sparkybuoy on August 6 2006 at 6:21 AM

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Sparkybuoy -- Auto Mechanic -- 93% Positive Feedback on 193 Car Accepts
20 years experience
Reply
August 6 12:36 PM (6 hours and 21 minutes and 46 seconds later)
         
Reply to Sparkybuoy's Post: Will this also cause the rear wheels to still turn forward when the trans is in reverse
Customer (name blocked for privacy)
Answer
August 6 1:50 PM (1 hour and 14 minutes and 7 seconds later)
         
REPLIEDCheck Mark

You'd have to look at the hydraulic circuit diagram and see but it is a possiblilty. If you look at those bulletin titles, you'll see one about a servo piston and that might be the one that actuates reverse.

Do BOTH wheels turn forward or one and the other the opposite direction?



Please click on ACCEPT if I've helped...it's how we get paid for our time answering questions-THANKS-you can still write back after you ACCEPT.

Sparkybuoy -- Auto Mechanic -- 93% Positive Feedback on 193 Car Accepts
20 years experience
Reply
August 9 11:11 PM (3 days and 9 hours later)
         
Reply to Sparkybuoy's Post: the wheels will only turn forward ( even in reverse) as long as there is no pressure on the wheels, if you put any pressure on the wheels it will not pull. I have now pulled the valve body and checked all the valves, check balls (even measured the thickness of the balls with a mic. Believe it not but there wasn`t even no clutch material in the VB like you find most of the time. I`m going to run a line pressure test as soon as I get the VB reinstalled. The other strange thing is that everything on the inside looks brand new. As far as I can tell this trans does not look like it has be rebuilt
Customer (name blocked for privacy)
Reply
August 9 11:18 PM (6 minutes and 53 seconds later)
         
Reply to Sparkybuoy's Post: the wheels will only turn forward ( even in reverse) as long as there is no pressure on the wheels, if you put any pressure on the wheels it will not pull. I have now pulled the valve body and checked all the valves, check balls (even measured the thickness of the balls with a mic. Believe it not but there wasn`t even no clutch material in the VB like you find most of the time. I`m going to run a line pressure test as soon as I get the VB reinstalled. The other strange thing is that everything on the inside looks brand new. As far as I can tell this trans does not look like it has be rebuilt
Customer (name blocked for privacy)
Answer
August 10 12:35 AM (1 hour and 16 minutes and 48 seconds later)
         
REPLIEDCheck Mark

Did you see the part of one of my replies above about the servo piston that actuates reverse?



Please click on ACCEPT if I've helped...it's how we get paid for our time answering questions-THANKS-you can still write back after you ACCEPT.

Sparkybuoy -- Auto Mechanic -- 93% Positive Feedback on 193 Car Accepts
20 years experience
Reply
August 10 7:14 PM (18 hours and 38 minutes and 56 seconds later)
         
Reply to Sparkybuoy's Post: I just wanted to let you know that when I removed the rear valve body I found one of the two screens to be crushed in its hole, I repaired the screen and then air pressured the trans while the VB was out and all checked to be very good with no leaks, reinstalled the VB and now the trans works like brand new all engagements and all shifts perfect. Thanks and lets hope it stays working good. Bill
Customer (name blocked for privacy)
Answer
August 10 7:32 PM (18 minutes and 58 seconds later)
         
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Sparkybuoy -- Auto Mechanic -- 93% Positive Feedback on 193 Car Accepts
20 years experience
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