Ducman82

can you take a G28 trans from a later car and stick it in an OB? and can you take a LSD unit from a auto and swap that in to an 5 speed?

thanks for looking at my noob question...


jake

Ducman82

must have been a real dumb question... :-(

GlenL

No and No.

OK. Anything is possible with time and money, but the gears don't fit and the trannies are different sizes and came with different torque tubes.

Landseer

Can we revisit the first no?

Or maybe the definition of OB (god help us).

Ducman, what year car is the OB? Is it for your 81?

I think there are two manual transmission lengths, pre- and post-mid 80, and associated TT lengths.

So if the 81 is the target car, won't the G28 be a direct fit?
(I hope so, because I've got some surgery beginning soonthat may include putting a late 80 forwards into an 84)


And if the target car is a true earlier car, say 79, the later tranny needs to come complete its TT, due to the length change that happened mid 80.
(Not sure on the crossmember compat)

I know GlenL has a lot of experience --- what am I missing here?


https://rennlist.com/forums/928-foru...-g28-13-a.html

Tom. M

My 82 track car just got the swap. It was running a S4 engine/single disc clutch/and early G28.08 transmission. I put a G28/55 (90 GT transmission) in a few months ago and it was a direct fit.

What I don't know is if the torque tube was the original one from the 82..or the one from the 91S4 engine.

Vilhuer

Gearbox type makes all the difference. If its G28/03 then TT and rear subframe is needed or TT center shaft needs to be modified. If its G28/05 or any later box model then any other '80+ MY box type is direct swap.

Ducman82

yes its my 81. I have been thinking about rebuilding the trans this winter, but if there is a better upgrade, or a stronger trans then why not do that instead. so the "early" G28's should drop in, but the later ones would require a TT as well? thanks for the info guys.

Landseer

No, actually, the opposite.

In mid-June 1980 the G28-03 was replaced with the G28-05. The WSM (section 30-02) indicates this corresponds with beginning of prodn for the 1981 model year. So you should have the new configuration TT with the G28-05 box and should be able to use transmissions from newer vehicles and retain your TT.

The thread link seems to indicate that with a little ingenuity the later boxes could even be rigged to fit the earlier cars with the early TT's, though Jim Bailey didn't think that was a particularly desireable way to go.

Several of us down here near Richmond are contemplating putting a salvage box that is in our hands (maybe even a G28-03, but TBD) into a slightly later car. The later car has a problem with second gear and needs some help.

Ducman82

when i first got the car i notices the "yellow mark of death" aka, a yellow paint pen mark from a junk yard on the diff cover. so it has been changed out before. was it just the cover or the whole trans i do not know. but at any case, im thinking of swapping. but, if the one i have ( i will check case numbers when i get a chance) is worth rebuilding then i can always do that. i just like to add better equipment if i can.

GlenL

An "OB" is 78 and 79.

I'm old skool, that's all.

An '81 will take that tranny.

Ducman82

a 80-81 is an SOB Semi Old Bugger

Landseer

Ducman, please don't go there ( James in 4,3,2,1....)

Take the good news on trans transplants and run!


On the trans case, look at the back cover of the diffy.

According to the manual, if you see hex head bolts, its G28-05 or newer.
If hex nuts over studs, likely to be G28-03.

Of course read the numbers underneath for confirmation.

ubercooper

In my 79 I am currently running an 86 Borg Warner box retrofitted with an LSD... so I'd say if your going to that much trouble you might as well do it right.
.02

Ducman82

Borg Warner box?

Landseer

85 on have borgwarner components for synchros instead of proprietary porsche two-piece dogteeth synchro rings according to a post by villhuer a while back. More reliable / less prone to damage. Ryan Perella is advertising one for sale right now from an 85.