transmission swap

[wildfelr]

I would like to discuss by ph 352-475-3190 transmission swap in my 1981 avanti II rqb 3263....ill be picking up the new 700r4 later this week and replace the original th350 w 104k miles........If you have actualy done this id like to talk....ive done it befor on other cars and hotrods but it never hurts to get all the info and advice befor i start next week....thanks ,,,,BILL

[plwindish]

wildfeir, just saw your post. Hopefully you got some input. Dan Booth from Nostalgic Motors is a great resource and will let you know exactly what is needed. I had a 200R4 put in my 76 RQB2392, replacing the TMH 400 trans. My trans shop recommended the 200R4 over the 700R4 because of the gearing in the 200R4 and the trans length being about identical to the TMH 400 trans. 4 yrs later and over 20,000 miles, the trans has worked out very well.

[WayneC]

Bill, I hope you'll do a writeup with pics as you do this swap, so the rest of us can see how it's accomplished and what parts

are needed.

Wayne

[boogieman]

I'm just curious. With gas being relatively cheap, what is the major attraction for the expense of changing over to an AOD trans?

My '79 cruises at 2100 rpm at 70 mph. Not high rpm by any standard. Haven't been able to check mileage but expect it to be

very acceptable given the nature of these cars.

Seems to me the expense of the swap could be better spent in and on other areas of the car, including into the gas tank.

The cost of the swap could pay for years of driving enjoyment.

My TH350 is bullet-proof and functions great.

But then I'm into highway cruising. My "hotrod" days far behind me.

[Gunslinger]

Swapping transmissions is a personal decision to be made based on factors that appeal to each person...or simply what he wants.

First...does anyone expect gasoline to stay at current levels for any extended period of time? That factors in.

If your car turns 2100 rpm's at 70 mph, I would expect your car has a numerically low rear axle ratio or the tach is inaccurate, which is not unusual. Either way...if you're happy with the way the car runs now, why change anything?

The expense of the swap may never pay for itself in fuel savings unless you keep the car for long term or use it as a daily driver...I think that's a given. On the other hand, whether it pays for itself or not, it does save wear and tear on the engine by reducing rpm's. Again...if that's important it's up to the owner.

For myself, when I purchased my '70, the BorgWarner PowerShift was leaking profusely. I discovered that to rebuild the BW was less cost-effective than installing a 700R4. The 700 also has an aluminum case rather than a cast iron case like the BW...less weight. I also had an aluminum driveshaft installed...again...less weight and less rotating mass.

I also seriously considered converting the car from an automatic to a Tremec 5-speed manual but would have been mucho more expensive than the 700R4 swap.

Again...whether or not to do a transmission swap is a personal decision based on the wants and needs of the owner. There's no wrong answer...just making yourself happy.

[plwindish]

Boogieman, my 76 with a 3:31 rear end was turning just about 3000 rpms @ 70 mph. With the 200R4 and same rear end, its barely turning 2000 RPM's at 70 MPH. The 1000 rpms make a big difference in engine noise and fuel economy. Driving 70 mph now will get me between 23 and 25 mpg. Before with the TMH 400, it was 14 to 14.5 mpg. Cost-wise, the trans shop rebuilt a 200R4 and installed it with me supplying the shift rods, tv cable,trans mount and new shift position indicator plate(sourced from Dan Booth) for $1600 in the Chicago suburbs. The total was at or just over $2000 adding the cost of the parts I supplied. I think it was well worth the cost to add the AOD.

[Avanti83]

The best part about the 700R4 and it's variants is availability. There is still an excellent chance of finding one in great condition, bolting it in and driving away. Not much chance with a 2004R anymore. If you need a rebuild then it's close to a toss up. The mount is pretty straight forward, If you want to use your existing mount, it can be trimmed, but the drive shaft will need to be shortened, However I'll bet a Camaro shaft would work, just measure the length and search the yards. So the cost doesn't need to be in the thousands if you don't want to spend that much.

I have a 2004R in my 83 but a 700R4 would have worked. Remember the 700R4 was offered in 83 so it will fit fine. Bob

Edited April 13, 2015 by Avanti83

[boogieman]

All sound reasons to make the swap. I am simply forwarding the conversation. Most of my MOPARs had 3.23 gears, which is

standard in most cases. Always preferring a forward rake on my cars, larger diameter rear tires helped both issues easily.

I have run 3.23's, 3.55's, 3.73's, 3.91's, 4.10's, and even 4.56's on the street. 440 ci Mopar's don't like short gears at all.

As I stated, my '79 has 3.08 gears and 27.75" tall tires giving 2000 -2100 rpm at 70 mph. Very long legged for sure.

The TH 350 can be rebuilt and guaranteed for about $600 - $700 depending on quality of parts.

Fortunately mine has only 50, 800 miles on it and works great with no sign of problems or leaking.

I'm very happy with my set-up.

Citing plwingish's situation, going to a taller rear gear could have lowered the rpm's by a like amount for far less than $2,000.

Your car, your choice, and I respect that.

And I certainly understand the case of replacing a cast iron unit.

With the torque multiplication in my TH350, 3.08 gears, and tall tires I can still haze the tires from a stop.

For me, the best of both performance positions. Smoky burnouts with great, easy, low rpm, relaxed cruising.

This is what makes cars so interesting. Everyone has their own interpretation of what their car should be.

Money and imagination the only limiting factors.

To each his own.

I have been involved with cars for 56 years now, since I was 10. I've come to appreciate them all and respect each one for the

time, effort, and monies (or lack there-of) used to express the owner's vision.

Obviously I have no intentions to make the change in #2897. I like it just as it is.

My curiosity wonders why so many choose to modify cars such as ours given the very low production numbers

and subsequent rarity and uniqueness.

I mean these aren't Camaros, Chevelles, Mustangs, or Mopars, or any other mass produced product.

[PackardV8]

My curiosity wonders why so many choose to modify cars such as ours given the very low production numbers

and subsequent rarity and uniqueness.

Because the Avanti II has the belly-button SBC and associated trannies, it's easy and cheap to bench race and tailor the car to one's own needs and tastes.

Also, I'd guess it's because Avanti are so dirt-cheap. There's no particular loss of value in modifying a car which is worth next to nothing to begin with.

I bow to no man in my love for Studebakers and Avanti. I just don't mistake low production and rarity with market value.

jack vines

Edited April 14, 2015 by PackardV8

[Avanti83]

Because the Avanti II has the belly-button SBC and associated trannies, it's easy and cheap to bench race and tailor the car to one's own needs and tastes.

Also, I'd guess it's because Avanti are so dirt-cheap. There's no particular loss of value in modifying a car which is worth next to nothing to begin with.

I bow to no man in my love for Studebakers and Avanti. I just don't mistake low production and rarity with market value.

jack vines

Absolutely, as well as the fact that Avanti Motors would do about anything to them to sell 'em, so they were the original modifiers.

To wit, my 74 4-speed should have had a 400 SBC, the OP didn't want no stinkin' truck motor so Altman put a 350 in it. If he wanted a available overdrive it would have magically appeared I'll bet. So how much more modified is it now with the t-56 replacing the 4-speed than when it was delivered from Avanti Motors with a 350.

The 66 and up were essentially modified cars from the factory if the OP asked for a non-standard change/addition.

Bob

[boogieman]

Point well made gentlemen.

As thrown together and cobbled from so many sources as they were, I choose to keep mine as Nate & Co. built it.

I like them all.

Other than using equipment not even conceived when these cars were built, go for it.

And you are so right about not much market value.

Nail that coffin shut.

[wildfelr]

iM BACK..(RQB3263) tranny swap update........I now understand why i got no replies for firsthand data on 700 in 350 out swap....I (we) did the job yesterday. I purchased the 700r4 from Lane Automatics in Ocala, Florida......Highly recommended...$1325 complete.....that was the easy part.......dont try this alone !!...Im sure I could not have done it without big, strong and most important knowledgeable help....a few tips befor i forget them....Remove dist cap (HEI only)....My drive shaft requires 2" shortning.....exhaust pipe on right side of tranny tooo tight (up against the tranny pan) and will need modification, this will req. small mod to frame holes where pipe goes thru.....350 dust cover does not fit 700 tranny (find a steel one)..you will need enough 3/8 extensions to get back 3 1/2 to 4 feel and flex sockets....drain the fluid ...and cap the tail shaft spline ,,,,cut the trans cooler lines in an area easy to reconnect with hose connectors... cut the kick down cable and remove (dont confuse it with the similar throttle cable youll be in big trouble)...even with a 4 post lift, stiff leg for the engine, and transmission jack, it was over 3 hrs. coming out..W got the new2 one up and bolted in in another 3 hrs or so......going in was easier then coming out....modification to the trans cross member req band sawing about 1" off each side and redrilling the 4 holes,,trial and error....well today is a day of recuperation and trip to driveshaft shop....many small hookup still to do over the next few days....keep em rollin....rqb3263 ....bill gregg

[wildfelr]

RQB 3263 WILDFELR.....Justa couple more things before i forget them.....The diagional steel bracket from the trans mount over to the exhaust pipe will be removed and discarded....caution....the bolts for the trans mount to the trans are METRIC on my trans and the bolts from the mount to the crossmember are SAE ...dont mix the up they look similure (the same)....also I shortened the metric bolts by 3/8 in so the wont bottom out in trans ...(its aluminum)....more later unless i forget......off to the driveshaft shop ......RQB3263.....BILL

[Avanti83]

Excellent followup BIll. Let us know your driving opinions and post a couple of pictures, if possible. Bob

[wildfelr]

RQB 3263...A relatively easy day today....new drive shaft ...(49 3/4 inch center to center) fit perfect and had better (more) spline engagement than the original...cost $153.00......dip stick tube can only be installed if the grommet is installed in trans first...we tried it the other way it wont fully engage...i installed an electrical bonding jumper from the metric trans mount bolt to chassis...a few other minor challenges.....but next and last challenge is the shift rod from the shifter to the trans... It appears the rod to the steering column will hook up with very minor adjustment but the shifter rod appears to need to be completely re fabricated......there is sure no extra room to work with....i would sure like to see what that rod looks like on any other 700 equipped avanti II......Chime in ...educate me before its too late....RQB3263,,,,BILL.

[plwindish]

Bill, one advantage of the 200R4 over the 700R4 was that the driveshaft did not need to be altered. Regarding the console shift indicator, Dan Booth has those in stock that can be swapped in for the old PRND21 and make it PRND321. How did you handle the lock up?

[wildfelr]

RQB 3263....Almost done.......all hookups complete today...lockup wired to a switch on dash....all setup by trans shop.....serviced with 11 qts at idle in park.....it has to be in park cuz the only thing i got left is the shift rod and its on order and should be here Saturday...No other linkage changes are required........So next week ...a trip to the muffler shop to move the exhaust from contact the right rear corner of the trans pan then to the trans shop in Ocala for final adjustment check........next project ....Air conditioning.....what ever it needs ....Adios for now ....RQB3263.....BILL

[wildfelr]

RQB3263.....TRANS SWAP COMPLETE.....but it req another mod (complete rework) to the trans mount crossmember...this raised the mount up 3/16 inch and centered it properly....this corrected contact between the speedo cable and the frame rail and eliminated slight drive train (drive shaft ??) vibration ...all smooth now ans maybe today ole 3263 will get new mufflers and the exhaust pipe moved to the right of the trans pan another inch...i will then have 1 inch clearance on the 700 trans right rear corner of the pan...the bigger trans caused this problem ....see ya on the boulevard ...rqb3263

[PackardV8]

The most important and difficult parts of the swap were seemingly the smallest and the last to go in on my conversion:

1. The shifter linkage needed to be from a 700R4 floor shift application. I was never happy with the modified 3-speed shifter.

2. The Throttle Valve Cable linkage on the carburetor ultimately was sourced from BowTieOverdrives. I was never satisfied with the home-brew bracket and linkage.

I also bought their pressure gauge and instruction kit. Getting the TV perfect is the key to a satisfactory driving experience.

3. GM has made dozens of governors for their auto trans which all shift at differing full-throttle RPMs. If the shift point is too low, find one from a smaller engine, usually a V6. If it holds the RPM too long, a larger engine governor is usually the cure. Governors can be modified, but most any tranny shop has a bucket full of GM governors. Smaller weights = higher shift point.

jack vines

[WayneC]

Nice discussion between folks who have done it before, glad it worked out for you... the rest of us are left completely baffled because no pictures, no links to hardware, and very brief cryptic verbiage (and I consider myself mechanically-inclined).

Bill, wish you'd have taken my prior comment to heart, I'd have liked to learn something about doing a swap from this thread, but I didn't. Opportunity missed.

[dstuff5]

someone had posted an itemized check list for removal and replacement of th4oo with 700r4 would like to see it again so I can print it. He said it took him about an hour???

[Avanti83]

someone had posted an itemized check list for removal and replacement of th4oo with 700r4 would like to see it again so I can print it. He said it took him about an hour???

I'd be shocked if you could do it in less than 5 hours and I'll bet a few more. 400 removal, piece of cake but they weigh a ton. IIRC reinstalling the R4 will require you change the position of the tranny mount and possibly narrow it and drill new holes in it. Not hard but consumes time. You will need to hookup the shifter and I'm not sure if the old one will give you all the gears in the new OD unit. You need to change the shift indicator also.

You will need to hookup the TV cable as there was not one on the 400. Driveshaft needs to be shortened and balanced also. The R4 requires a way to lockup the converter if you chose to use one. I'd suggest you do unless you buy a trans/converter setup to not need it. You can use a simple 12v switched supply and lock the converter on the highway only. That's what I do.

Just some thoughts quickly, probably more I haven't thought of.

Edited May 15, 2016 by Avanti83

[Gunslinger]

You do need to replace the shifter quadrant as it and the shifter dial are different. You can use the original shifter but the detents won't line up with the shifter dial...you need to be aware of the detents compared to the indicator dial...better off buying the right shifter as well.

[silverstude]

I did mine back in the late 90's and if memory serves me correctly, the exhaust pipes have to be tweaked to go thru the frame, a new rear motor mount is required, (which is where I found that GM used some metric bolts on things). My shifter came out of a 97 Camaro and was installed on a trans tunnel floor which had to be fabricated. After that the exhaust pipes were wrapped with Thermotec to avoid frying the shifter cable.

Since I was using an R3 airbox, a hybrid mount had to be made for a Lokar TV cable, plus a unique piece of throttle linkage.

I also went to BowTie Overdrives for help and they were great to work with. They produced a kit to make everything work like a clock. The car was placed on jackstands and a new TV shifter spring was installed. A transmission pressure gauge was attached and it was run through the gears at specific RPM's to check shift points. Everything was noted and a call to BowTie was made, after which they advised on TV cable adjustments. You need a specific TV pressure range to make the shifts properly. Beyond that, the transmission was modified to have the lock-up only occur in 4th, plus put a switch on the dash to activate it or not..

An auxiliary oil cooler was added ( due to paranoia about heat) ......

[dstuff5]

Gunslinger was RIGHT on time for removal only (took over 5 hours) and I'll still have to cut exhaust pipe (had it custom built for TH400 and will have to

resection it for right side clearance. before I cut it anybody with any input all help deeply appreciated.

Thanks, Dave