5-Speed manual Transmission Fluid Type

[SteveNixon]

Just inherited a 1989 Chev C1500 Reg Cab. with 4.3L TBI and 5speed manual.

Looked through all his old files on the truck, and couldn't find the maintenance or owners manual.

Thinking of doing a fluid change in the tranny. What type of fluid do I need?

I'm pretty sure it would be Dexron III, but last I checked it's hard to find now.

Any help is appreciated.
Thank you
Stephen

[Airjer_]

I would bet its 80/90 gear lube.

[wafrederick]

Takes special fluid from the dealer only.

[Airjer_]

I just checked amsoils lube guide and 3 out of the five transmissions offered do take synchromesh (gm special fluid). I didn't think they used that until the 90's.

[MT-2500]

Originally Posted by SteveNixon

Just inherited a 1989 Chev C1500 Reg Cab. with 4.3L TBI and 5speed manual.

Looked through all his old files on the truck, and couldn't find the maintenance or owners manual.

Thinking of doing a fluid change in the tranny. What type of fluid do I need?

I'm pretty sure it would be Dexron III, but last I checked it's hard to find now.

Any help is appreciated.
Thank you
Stephen

You need to ID your transmission.

77mm 0r 85mm transmission?

77mm calls for dexron11

4 & 5 speed 85mm transmissions use gm std. transmissin fluid

Carquest has dexron/mercon transmission fluid.

Gm parts places have the GM std transmission fluid.

[j cAT]

Originally Posted by SteveNixon

Just inherited a 1989 Chev C1500 Reg Cab. with 4.3L TBI and 5speed manual.

Looked through all his old files on the truck, and couldn't find the maintenance or owners manual.

Thinking of doing a fluid change in the tranny. What type of fluid do I need?

I'm pretty sure it would be Dexron III, but last I checked it's hard to find now.

Any help is appreciated.
Thank you
Stephen

I had this question with the 5speed manual in a 1994 S10..the fluid spec is dexron III...as you know this is no longer available so for a time only dealers had the replacement ,,,this is synchromesh fluid....this is now available at advanced auto ...I just got some the other day...dealers also have it but tooooo pricy for me...

[MT-2500]

Originally Posted by j cAT

I had this question with the 5speed manual in a 1994 S10..the fluid spec is dexron III...as you know this is no longer available so for a time only dealers had the replacement ,,,this is synchromesh fluid....this is now available at advanced auto ...I just got some the other day...dealers also have it but tooooo pricy for me...

Synchromesh fluid and dexron-dexron 11-dexron 111 is two different fluids.

Be sure to ID transmission for proper fluid.
Back in 89 if dexron was used in it it was dexron 11
Carquest has dexron/mercon transmission fluid

[j cAT]

Originally Posted by MT-2500

Synchromesh fluid and dexron-dexron 11-dexron 111 is two different fluids.

Be sure to ID transmission for proper fluid.
Back in 89 if dexron was used in it it was dexron 11
Carquest has dexron/mercon transmission fluid

one thing I do know is I checked this out very very carefully...in the 5 speed transmission that calls for dexron III synchromesh is now the replacement fluid...this was checked at more than one dealership , and the spec on the bottle of the synchromesh fluid...[pennsoil]

now I can tell with all certainty that the new dexron VI is not dexron III,,,this is a very synthetic type of fluid,,,and as you know the yellow metal in these 5 speed transmissons need special fluids...

can't comment on dexron II....but I would guess it is very simular to dexron III..

with a vehicle this old one has to be very certain before using / guessing at what to use...
synchromesh fluid is good for these GM numbers equivalent to GM Part No. 12345349 or 12345577

just found this :HM-290/5LM60 5-speed manual transmission - Synchromesh transmission fluid P/N 12345349


this transmission was used during the late 80's in the light duty trucks..