Differences between 85 and 86 4+3 tranny?
Thread Starter
Racer
Joined: Jul 2009
Posts: 454
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From: None None
Differences between 85 and 86 4+3 tranny?
Hi. Im looking at buying a rebuilt 4+3 tranny out of an 86 Vette. The asking price is $600. Reason for buying is because my tranny in my 85 acts up a lot and grinds 2nd gear randomly. Also, the OD unit also has a mind of its own as they all do.
What Im asking is are there any major differences between the two year trannys? Are they more durable? Better performance? Will it bolt up properly to my 85? is $600 a good price?
Any input greatly appreciated
-Thanks
What Im asking is are there any major differences between the two year trannys? Are they more durable? Better performance? Will it bolt up properly to my 85? is $600 a good price?
Any input greatly appreciated
-Thanks
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
major difference between 85 and 86 o/d makes the 86+ much more durable...$600 is cheap $ IF it's a good used unit...and if it's a 'z51' 4-3 it has several extras that add durability, also better o/d ratio
Last edited by redrose; Nov 7, 2009 at 08:29 PM.
Thread Starter
Racer
Joined: Jul 2009
Posts: 454
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From: None None
Thanks for the info. Ill be sure to ask if its from a Z51. Will it directly bolt on to my 85? My car is a Z51 if that makes a difference.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
will bolt in but 86+ do not use the 'third cable' that runs from trans to throttlebody...sorry i can't remember (old age - mind is second to go) but likely some 'ecm issues' of o/d control (go 'manual' o/d selector switch to defeat that)...only way to tell visually if trans is a z51 unit is id tag on o/d pan bolt + factory production records (who has these ?), during actual drive the o/d rpm drop differs a bit from base vs z51.
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Joined: Sep 2009
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will bolt in but 86+ do not use the 'third cable' that runs from trans to throttlebody...sorry i can't remember (old age - mind is second to go) but likely some 'ecm issues' of o/d control (go 'manual' o/d selector switch to defeat that)...only way to tell visually if trans is a z51 unit is id tag on o/d pan bolt + factory production records (who has these ?), during actual drive the o/d rpm drop differs a bit from base vs z51.
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Joined: Feb 2005
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From: Balsta
Le Mans Master
Joined: Aug 2000
Posts: 8,838
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From: Australia
http://www.5speeds.com/43table.htm
These are done by the programming in the ECM; obviously your '85 won't have the same programing as the '86 .Worst case if ECM control is a problem ,the O/d relay can be manually switched so you have total control of the O/d ; most people only engage on the open road
Use the side cover off your 85 to retain the 1st gear switch; '86 doesn't have one
O/d ratios
MH5: 0.62
MK2: 0.68 ( Z51)
Last edited by rodj; Nov 8, 2009 at 06:08 AM.
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Melting Slicks
Joined: Apr 2007
Posts: 2,616
Likes: 111
are you sure you would not to consider the Keisler 5 speed kit made for your car? They apparently have everything for the swap....just an idea....from what I hear they are much more durable transmissions with a flush market of parts for them.....(unlike the ZF).....
Thread Starter
Racer
Joined: Jul 2009
Posts: 454
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From: None None
That would be great...aren't those kits big $$$ though.
Melting Slicks
Joined: Aug 2003
Posts: 3,395
Likes: 393
From: Lakeville MI
The first gear look ahead ok tps threshold is also more sensitive in Z51s (25% vs 40%) to make Z51s more likely to remain in direct drive on drive off.
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
I have a 88 OD in my 85, it does not have the cable and everything works great, including the kickdown. My 4 speed portion is original. The TPS threshold thing is interesting, (mine is a z51) and I was unaware of that. It does not want to go into OD after a good romp on the pedal up the freeway onramp. I am unsure of the value of this, and am wondering if this can be tuned out of the chip?
