TH400 to 700-R4 Trans Swap

[Skyguy007]

I have a '69 BB with the original TH400. I've read the literature about swapping in a 700-R4 to get an overdrive with a lock-up torque converter and a lower (higher ratio) first gear. Bow Tie Overdrives looks like the way to go for different levels of transmission bullet-proofing and the rest of the parts needed to do the swap. I'd be interested in hearing from anyone who has experience with BowTie or just doing the swap. It looks like a $1,500.00 job that will totally improve the top and bottom ends of my Vette's performance curve. Is this too good to be true?

 

[LUDS96]

The Stock trans is 700 R4 L60 I thinks there is a L80 Higher torque to handle that Big Block the turbo 400 is almost bullit proof so look into it. It's probably a Truck model.

 

[BlackNBlue95]

Huh?

Well the 4L60 is basically the 700R4 for starters and the 4L80 I thought was the same as the Turbo400 trans but I am not 100% shure on that I do know that the 4L80E is a stronger trans then the 4L60E but it's also bigger and heavier in size. the numbering / nameing scheme GM started using in the early mid 90's basically ment that the higher the number 4L60 vs 4L80 means that the 4L80 can handle more torq. something that I was taught in my trans class a year ago.. maybe I'm wrong. just my 2 cents for ya..
-Rick

 

[page62]

Send an email to Bowtie. Or better yet, go to their website and fill out an inquiry form. They will send an extremely detailed response. They care about you before and after the sale.

I know. I've done it. I'm very happy!

 

[LUDS96]

TH400-700 r4 trans swap

Vette Magazinre had an article on this swap Last Year

 

[crebo]

What is going on SkyGuy. I went to the 700r4 thru Bow-Tie. I also have a bb. I haven't had any problems so far.
It's hard for me to comment on the perf. I had a 350/350trans. One month later BB 402/700r4. I've only had the trans with the big block. I have a level 2. Didn't check to see where you're from. They have pretty strict rules to keep your warranty. If you go to there shop they'll give you a ride in a beater........with a level two trans. They drive it like a mad man.
I drive mine pretty hard again no problems yet. I turn about 2500 at 85 mph. I still have the stock 3:08 rear. Looking to upgrade to a 3:70
hope I helped alittle. If you have more specific questions just send them and I'll do my best
Crebo

 

[Bob Yates]

I did a swap in my 81 and the 700R4 was a great move. I'm told you need a 1988 an up they have all the bugs out of them. I did my swap for around $1500.00. Call Fourth Gear Inc. and talk to Don Marcone he does a good job of updating and rebuilding the 700R4's. Phone # 407-880-2882.

 

[zZArAZz]

I did the conversion on my 1981 about 7 years ago. It was great for a low horsepower highway vette. However I went through 2 different transmissions because second gear kept giving up.
It also was hard to get to stay in 4th gear. These days if they make a stronger 700r4 it would be great. I am right now doing the switch back to a 400 turbo to handle the power of my upcoming 505 bb install

 

[zZArAZz]

Here is a info chart on transmission specs I borrowed from a similar post on a different forum

http://www.gnttype.org/techarea/transmission/transtutor.html

 

[Last Ride]

Just out of curiosity, what will you do with the old TH400 when you get the new unit? I might be interested if you deicde to sell it. By the way, I have a 4L60E mated to the LT1 in my 78 and I like it.

 

[Skyguy007]

If I ever do the swap I'll probably have the old TH400 rebuilt and stored. It's liable to be sometime before I even think of doing that, though. My project of the month is to replace the old, as in leaky, radiator with a new aluminum look-alike. I'm hanging on to the old radiator too. After all is said and done, I'll have about $700 invested in this project. (and right before Christmas too...ouch!)

 

[WayneLBurnham]

Have you considered another OD?

I desperately need an OD now that I had the 3.70 put in on the 12 bolt.

Since the whole reason I got into this red sinkhole for money was to have a home for a monster BB I have to build before I expire, I was concerned about a tranny that could handle the torque.

The poster was right - the 4L60 (700R) is a "4" Speed "600" ft-lbs of torque rated thingy - from the factory. This was VERY optimistic in the earlier models from everyone I can find out anything from. Early or junkyard 700R's are frail indeed.

The 4L80 is MORE than just an OD on a Turbo 400. It is rated at 800, and this rating was probably understated, but it is ENORMOUS and HEAVY - about 125 pounds heavier than the 350 and dimensionally larger even in the aft-of-bellhousing area. (It had been my choice on paper, until I found out all this badness.)

The good news is a number of companies have greatly improved the 700R/4L60 over the later factory redesign even, bringing it up to a useful 800 ft lbs use, and not intermittently either, although most of those go for $1200-1900, just for the tranny.

The route I am planning on going though offers even more power handling and all the electronics are self-contained (a problem with the massive 4L80.) I am - and would already of done it, if a minor rear axle didn't decide it's number was up - putting in a Gear Vendors OD unit.

Installation of this thing does not sound as simple as a tranny swap, but they were downright insulting at GV when I told them I had a tranny guy who was going to do the install for me for $750.
They claim it's easily done by any moron.

They describe it as a "coffee can" sized thingy that bolts on in place of the tailstock on your T400. Aside from dropping the tranny - or even just tilting it, you have to notch two squares in the glass at the rear of the tunnel and have the driveshaft length changed at a driveshaft shop - and run a place for a switch. (You will normally need to do that in any tranny switch anyhow.)

I hope to see as soon as the OverDrive Fairy leaves me the buckaroos under my VettePillow.

Besides being rated at 1250+ ft-lbs in the regular form (more than a stock T400,) they offer not just an overdrive, but a true 6 speed automatic function. The unit functions as a gear splitter as well as bolting on a 70% drive on top. So you get the close ratio shifting of a 6-speed like out of a nicely equipped C5, although your top ratio is .7, not .5 - but no clutch to burn out in six weeks of careful abuse!

The price of these puppies is about $2300 raw - my tranny guy would charge another $800 or so, so I'll just get my fat gut crushed under the car sometime this spring, hopefully.

Just more choices!!!

 

[MaineShark]

Re: Have you considered another OD?

Besides being rated at 1250+ ft-lbs in the regular form (more than a stock T400,) they offer not just an overdrive, but a true 6 speed automatic function.

You might want to double-check, but I looked at this unit earlier, and I believe that "auto" function only gives you 4 gears (the regular three of the transmission, plus OD). For 6 speed, you would have to switch it to manual mode, and trigger it between gear shifts as you upshifted.

I'm wondering if anyone has developed a reprogrammed computer for the 4L60 that could control the GearVendors unit, giving true 6-speed shifting. A manual mode, with paddles under the steering wheel (ala Ferrari) would be even cooler

Joe

 

[WayneLBurnham]

Not sure on function mode

You may be right - I haven't looked at the GV 'site in a few months now. It's possible the 1st-1stSplit-2nd-2ndSplit-3rd-4th only works in Manual override (although that's pretty much how I usually shift the T400 now anyhow )

I do recall they mention the performance choice is usually to skip "1stSplit" with anything over 500hp to limit wheel spin.

The strongest of upgrades for T350's and T400's use a full manual valve body anyhow, but I think you can get to the 1250 ft-lb strength mark w/o having to go that route.

They do offer units directly for both the 4L60 and 4L80, so I assume they have full function with their electronics, although I think it routes through the GV unit controller first rather than the 4L60/4L80 being the host.

I'm not familiar with the Ferrari system. In "unusual tranny rigs," I only played with a Lenco driven beast once (and that was enough!) other than that I would be THRILLED just to have more gears! It would seem you could rig a mode switch somewhere on the wheel or column or shifter fairly easily - and even cosmetically decently.

One cool switch arrangement I was thinking of was the new PainLess Wiring 4-Button RF (?) horn button controller thing. Originally I had planned on putting any activation switches on the shifter, but since I wanted to switch to a Flaming River shortened column and 12.5-13" wheel anyhow, I saw the new PW system as ideal for these switches, sound mute, N2O and something else.

 

[MaineShark]

The Ferrari system is essentially a manual transmission, outfitted with servos to operate the shifter and clutch. So, you have a real clutch (no power wasted in the torque converter) but the computer handles it. All you have to do is tap the "up" or "down" button, and it shifts. Or, if you get lazy, you can flip a switch, and the computer takes care of that, too. Nice system, but a bit pricey

With some modifications to the 4L60's transmission computer, a pair of buttons could be added, to force the transmission to shift, same as using the shifter, but without having to reach down. Of course, you would have a torque converter, not a clutch, but you would have many of the other benefits.

I believe I heard of an aftermarket replacement computer for one of the Ford transmissions to do this, but I can't remember where.

Joe

 

[Bob86ZZ4]

Gear Vendors

I put a th400 manual valve body/Gear Vendors in my '86 last winter. I drove all summer with it. It is awsum! I like it very much. I never use the auto feature of the overdrive electronics. I think what that does is just engage the od unit at about 45-50 mph, no matter what gear your tranny is in. For autocrossing and road racing this is the best thing you can do if you have lots of horsepower and don't have a ZF6. The Gear Vendor shifts are instant and very firm. Downshifting is the same. In most driving I use engage the Gear Vendor if I want a little more gear and know I'm not going to need the next th400 gear. In autocrossing it is great for giving just the right gear to get to the next cone. Check out my web site for how I put mine in. I am by no means a skilled mechanic and I managed to get it in. The guys at Gear Vendors were very helpful to me on the phone. They said I should be able to cut and re-drill my torque arm but I messed that up so I just designed and fabricated my own torque arm. I made a 2 piece one and it's very easy to take in and out now. I highly recommend doing this conversion. Oh ya, I put on a B&M shift handle with the little push button on the side for doing the Gear Vendor in/out shifts. It works great. Good Luck.

 

[WayneLBurnham]

GREAT BOB!!!! I Needed To HEar This!!!

Thanks for the news guy!!!

I'll check out your website shortly!!!

I was already going to put this wee little darlin' on my POS, but it decided it needed to ditch a rear wheel assy at the middle of the axle last month...

What was your total est cost?

Your newest bestest buddy!

 

[Bob86ZZ4]

Wayne

The Gear Vendors setup for a C4 is a little bit more than a C3 because it has the fittings for the torque arm. I would think the install would be easier in a C3 also. I bought my tranny from a shop in Delaware for $1400 with the torque converter. My parts total was about $4000. But remember, now if my th400 craps out that should only cost me about $500 to get completely rebuilt. And I already told about the warranty on the Gear Vendors unit. Good Luck.

 

[Skyguy007]

While the overdrive setup sounds like a fun way to go for those with deep pockets, the Bowtieoverdrive strengthened TH700 sounds like a much less expensive alternative for street use on a fairly stock '69 BB.