4+3 ----- Problem
Thread Starter
Intermediate
Joined: Jun 2017
Posts: 34
Likes: 1
From: Cincinnati Ohio
4+3 ----- Problem
I have an 85 vette with a 4+3 that runs fine. I have a spare 85 4+3 that I bought in 1998. It has always been stored inside and came from a wreck.. Existing OD fluid was not dark or burnt.
I changed the fluid and filter.
In non OD mode, it shifts thru all 4 forward gears and reverse works fine also. Ist gear is locked out of OD, when in second and apply power to the OD solenoid, it locks the rear wheels.
I believe the clutches may be stuck to put it into OD. Dunno, I will run it a while without OD to see if it eventualy unsticks.
Any input is appreciated.
I changed the fluid and filter.
In non OD mode, it shifts thru all 4 forward gears and reverse works fine also. Ist gear is locked out of OD, when in second and apply power to the OD solenoid, it locks the rear wheels.
I believe the clutches may be stuck to put it into OD. Dunno, I will run it a while without OD to see if it eventualy unsticks.
Any input is appreciated.
Last edited by Dennis L Brooks; May 14, 2020 at 05:11 PM.
Le Mans Master
Joined: Sep 2009
Posts: 6,343
Likes: 1,149
From: Vermilion OH
It seems to me that the bearings on the current overdrive unit have seized. I'm just making an educated guess but if everything is fine until the overdrive unit is engaged, the issue lies in the overdrive unit. If its locking the rear wheels, it may be seized.
Thread Starter
Intermediate
Joined: Jun 2017
Posts: 34
Likes: 1
From: Cincinnati Ohio
Thankyou, I was looking for educated quesses. It is not easy finding a whole lot about it on the web. It looks to have 2 or 3 sets of clutches in it from web youtubes. I am not using the TV cable and as I understand it does not work like it would on a 700R4 trans. It just kicks it out of OD on heavy acceleration and maybe cushions shifts. The trans make no noticeable noise in any gear so I will run for a while, warm it up and then eventually try the OD again.
Safety Car
Joined: Oct 2007
Posts: 4,426
Likes: 229
From: Pennsylvania
Normally, when an overdrive unit fails (most always from service/maintenance neglect) the overdrive unit will not function at all. The overdrive will free wheel and it won't have any effect on the rear wheels at all. Locking up the back wheels to actually skid the car to a stop is a new one on me. I agree with mazdaverx7 with the bearings being seized up. I just can't figure how this could have happened without some sort of pre-failure indications.
Thread Starter
Intermediate
Joined: Jun 2017
Posts: 34
Likes: 1
From: Cincinnati Ohio
Yea, I was not expecting my result. If I flip the OD on it skids rear wheels and before I stop I flip it off and all is well. I will drive it for a while to see if it may be a free fix.
I will let you know but may take a while. I am fan of the 4+3 and like the one in my 85 ( purchased in 1997) but I know it has its limitations. 8-)
Looking at GearBoxVideo again, I am guessing that the Direct clutchpack is not releasing when the OD pressure to outer clutch pack is applied.
I will let you know but may take a while. I am fan of the 4+3 and like the one in my 85 ( purchased in 1997) but I know it has its limitations. 8-)
Looking at GearBoxVideo again, I am guessing that the Direct clutchpack is not releasing when the OD pressure to outer clutch pack is applied.
Last edited by Dennis L Brooks; May 15, 2020 at 07:13 PM. Reason: words
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Thread Starter
Intermediate
Joined: Jun 2017
Posts: 34
Likes: 1
From: Cincinnati Ohio
Today, update on the OD problem. I disconnected the OD connection and have been driving with just low range - direct drive. No problems.
I am going to pull the 4+3 and put in a 350TH with a NP208 so before I do that I wanted to see if it would go in and out of OD. I hooked the 12v switch back up to the OD.
Once in second gear I clutched then I applied voltage to the OD . Vehicle slowed slightly then it engaged in OD. It shifts in and out now fine. I may have been correct in that once the OD clutches were activated the direct drive clutches did not release -- thus locking trans. This was because even tho trans was stored inside -- the direct drive clutches stuck probably because I had drained the fluid, changed the filter but did not refill it for 5-8 years. Dunno
All seems well.
I am going to pull the 4+3 and put in a 350TH with a NP208 so before I do that I wanted to see if it would go in and out of OD. I hooked the 12v switch back up to the OD.
Once in second gear I clutched then I applied voltage to the OD . Vehicle slowed slightly then it engaged in OD. It shifts in and out now fine. I may have been correct in that once the OD clutches were activated the direct drive clutches did not release -- thus locking trans. This was because even tho trans was stored inside -- the direct drive clutches stuck probably because I had drained the fluid, changed the filter but did not refill it for 5-8 years. Dunno
All seems well.
Last edited by Dennis L Brooks; Sep 25, 2020 at 04:52 PM. Reason: words