Avanti trans swap ????

[dclewallen]

I've got a 66 Avanti II with a stock Borg/Warner 2nd gear start transission. Its been acting up a little and the transmission shop I went to suggested a TH350 swap. I DO NOT WANT AN OVERDRIVE TRANSMISSION. Sorry thought I'd get that out of the way to save a lot of unessessary posting. My question is, What is involved in doing this swap? crossmember, flexplate, torque converter. linkages, driveshaft, etc. Have any of you done this swap if so what did you encounter? Thanks for any help/tips you could give me. DCL

[Gunslinger]

I recently had the 700R4 swap done in my '70 for the Borg-Warner and can give you some insight. Some would be the same, maybe some would not.

Essentially, what I found out was to rebuild the BW would, for all intents and purposes, cost as much as the swap to a 700R4. About the only major difference was the need for a new driveshaft. The change to a TH350 may require a new driveshaft as well...that I don't know.

The transmission support required relocating, but that was no problem. Just mark and drill holes for the new location and bolt it in.

The TH350 may or may not require modifications to the transmission tunnel. It seems some people have had to do so and some didn't. The 700R4 swap for me didn't require any. The linkages had to be fabricated as well as the neutral safety switch and back-up light switch as the originals wouldn't work with the swap.

You'll need a new flexplate but they're pretty inexpensive. You'll also need a new torque converter...not inexpensive but not prohibitively so. One may come provided with a transmission.

When you buy a new driveshaft, you can get an aluminum unit. A bit more expensive but worth the money. It reduces weight off the car and reduces rotating mass the engine has to turn over.

The TH350, as the 700R4, requires a vacuum hookup to the engine intake manifold. Not a problem but you'll have to tap into an exisiting vaccum line or install a fitting on the intake which would be the preferable course.

Check with Dan Booth at Nostalgic Motors or Jon Myers of Myers Studebaker...they can give you all the advice you need about what's required and probably have most of the conversion parts in stock.

[SBCA96]

The 700R4 doesnt have a vacuum control, its a TV cable hookup. Older TH350

transmissions had the vacuum, but I am pretty sure later ones went to a cable

as well. Regardless, this topic was done to death on the SDC forum and some

very good points were made. The point thats worth repeating here is :

Its NOT worth going through the cost and hassle to put a TH350 trans into an

Avanti with a Powershift transmission. The Powershift is a better transmission

in just about everyway imaginable. The rebuild kits are available and any tech

thats ever rebuilt an older Ford BW unit can do the work. There are also a few

Studebaker vendors that will do it for you. The ONLY reason to go through all

that work and money is to reap the cost savings of a GM OD trans. If you do

not drive the car enough to benefit from an OD trans, you wont have to worry

about rebuilding your Powershift ever again.

Its interesting you mention a 2nd gear start, unless I am mistaken the PS is a

1st gear start trans. So if yours starts in 2nd, it might be a plain Flight-O-Matic

in which case a TH350 would be an improvement. Info here :

http://www.studebaker-info.org/rjtechx3.html#Transmissions

Tom

[ernier]

I think you need to dive in...some of the hurdles you encounter may only be resolved by trial and error.

I had a 74 El Camino a while back and needed a trans. I bought a TH 350 on ebay from a company named Jackson Racing. I think it was under $600 with a 2000 RPM stall converter. Great service and great shifting trans.

There are different flexplates that Chevy engines use, external and internal balance and different diameters. You may have to pull your car apart to determine which you need. Also, the driveshaft length can only be checked once the trans is in along with proper placement of the crossmember. I believe there are long and short tailshaft TH350's.

The vacuum hook up for the modulator is easy, right to the intake manifold. The kickdown cable is not as complicated as the 200 or the 700 but you would still need a carb that has the hole on the linkage for the cable to connect to.

The clearance problem with the 700 is the servo, the TH350's servo is in roughly the same place. I don't know if the 350 is as wide but again until you stick it up there you won't know.

A company named Kugle Shiftworks makes an adapter kit that should enable you to use your stock shifter in place of the GM cable that the trans is commonly shifted with.

It's wise to seek advice but it seems from the responses that the O/D swap is more common than the TH350 so you may have to break some new ground. The good news is that we know it can be done and the TH350 is probably the least expensive trans you could choose.

Ernie 64 R2 700R4

I've got a 66 Avanti II with a stock Borg/Warner 2nd gear start transission. Its been acting up a little and the transmission shop I went to suggested a TH350 swap. I DO NOT WANT AN OVERDRIVE TRANSMISSION. Sorry thought I'd get that out of the way to save a lot of unessessary posting. My question is, What is involved in doing this swap? crossmember, flexplate, torque converter. linkages, driveshaft, etc. Have any of you done this swap if so what did you encounter? Thanks for any help/tips you could give me. DCL