home register FAQ memberlist calendar

Go Back   Turbobricks Forums > Mechanical > maintenance & nonperformance

Reply
 
Thread Tools Display Modes
Old 02-16-2021, 12:54 PM   #1
StuSims
Newbie
 
Join Date: Dec 2020
Location: canada eh
Question m46 P-Type Laycock OD slippage??

Hey all, Ive been having some mechanical gremlins plague my m46 transmission on my 1986 740 Turbo. One day I did a burnout at my house, and it worked no problem. Two weeks later after sitting since the last burnout, I decided to do another burnout to celebrate my birthday. There was a lot of noise and no spin, I had assumed I fried the clutch! It was still able to drive, but only very slowly with low throttle input (and for some reason, reverse worked like normal). Any more than 40% throttle, the car would rev up and not go anywhere. I replaced the clutch with a brand new Sachs clutch kit, and re surfaced the flywheel. The problem persists. . ive been told it is the cone clutches in the m46 OD unit? This would explain why reverse works fine, with the unidirectional sprag clutch. But after talking to a few transmission techs who are familiar with the Laycock OD system, they find it quite odd that all my forward gears are slipping. They think that a worn out cone clutch in the OD would only cause slipping in 5th gear. So, I have come to the all mighty TurboBricks for an explanation. Is anyone experienced with the Laycock overdrive systems in these cars? is my problem due to the cone clutch? Or did I pop an O-ring on one of the hydraulic pistons? Perhaps the internals of my trans have decided to run away? In search of a better life. Any help is appreciated.
StuSims is offline   Reply With Quote
Old 02-16-2021, 01:30 PM   #2
hiperfauto
The Librarian
 
hiperfauto's Avatar
 
Join Date: Nov 2011
Location: So Cal
Default

The unidirectional clutch transmits all the power in 1st-4th. The cone clutch inner surface is for reverse and engine braking. The outer surface is strictly for over drive. You either broke the unidirectional clutch or broke/stripped the splines on the main shaft.
hiperfauto is offline   Reply With Quote
Old 02-16-2021, 06:06 PM   #3
tintintin
Board Member
 
Join Date: Sep 2012
Default

^+1^


Quote:
Originally Posted by StuSims View Post
Or did I pop an O-ring on one of the hydraulic pistons?
That wouldn't cause this problem, as those pistons convert the hydraulic pressure to engage OD only.
tintintin is offline   Reply With Quote
Old 02-16-2021, 10:40 PM   #4
StuSims
Newbie
 
Join Date: Dec 2020
Location: canada eh
Default

Alright thanks guys! Anyone know if the P and J type OD units are interchangeable? My car is a 86 turbo so I’d assume it’s a P type. A buddy of mine has a J type. Could I swap some parts over to make vroom vroom??
StuSims is offline   Reply With Quote
Old 02-16-2021, 11:14 PM   #5
hiperfauto
The Librarian
 
hiperfauto's Avatar
 
Join Date: Nov 2011
Location: So Cal
Default

I believe the P type main shaft is larger so you can't mix and match.

The P type is supposed to be stronger than the J so I find it curious that yours broke. Your car should have come with a P type but it may have been swapped with a J type in the past.
hiperfauto is offline   Reply With Quote
Old 02-24-2021, 10:03 PM   #6
745T+
Board Member
 
745T+'s Avatar
 
Join Date: Feb 2003
Location: Vancouver, WA USA
Default

Quote:
Originally Posted by hiperfauto View Post
I believe the P type main shaft is larger so you can't mix and match.

The P type is supposed to be stronger than the J so I find it curious that yours broke. Your car should have come with a P type but it may have been swapped with a J type in the past.
Correct, they won't interchange. My 1986 "New Car Features" green book shows the P type being new for certain (turbo) models in 1986. There were also J/P type, and P/J type ODs. I don't remember the differences, but the P/J was used starting with a running change in the 1990 model year. The one new factory replacement M46 I had, had a J/P type OD.
745T+ is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -4. The time now is 05:18 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.