New Transmission

[Jr. Corvette]

Hey guys,

After driving the car this season I had a lot of fun but I think the factory TH400 is taking some fun away. It turns 3200 rpm cruising on the highway, has a bad clunk into reverse, I'm not sure about you guys but shifting into 1st from second sounds like the trans dropped out of the car, wide gear ratios make accelerating feel slow and third feels like a dreadfull lug.

I have been pouring over tons of forums and websites trying to find a nice transmission. My future goals are 700-800hp so I'd like a transmission that is capable of that. I would also like to do some highway driving so a nice OD would be nessesary for fuel economy and headaches. I don't launch the car too much but I'd still like to on occation and not be worried about the transmission. I would like to do road corse so I'd like at least some control over shifts on occation.

At first I thought about the T56 or even TKO 600 with a double clutch setup. Still would be interested in this but a strong enough transmission costs big bucks, then extra $1500 plus bellhousing in converstion costs. It fits all my criteria though so I may just have to bite the bullet. With the tight foot wells is shifting a hassle?

So what would you guys recommend?

Thanks in advance.

 

[turbozig]

It all depends on your preference auto to standard. If auto, and if looking for a reasonably priced alternative, I would go with a 700R4 from an early 87 or 88 GM truck, no electronics and cable driven speedometer. These are reasonably priced when built up for performance and can handle allot more power than the 200R4. It should fit your application with only a driveshaft modification. Too bad, I just got rid of one dirt cheap early this year.

 

[Jr. Corvette]

It all depends on your preference auto to standard. If auto, and if looking for a reasonably priced alternative, I would go with a 700R4 from an early 87 or 88 GM truck, no electronics and cable driven speedometer. These are reasonably priced when built up for performance and can handle allot more power than the 200R4. It should fit your application with only a driveshaft modification. Too bad, I just got rid of one dirt cheap early this year.

Thanks for the advice! I do have some problems with the 700r4 though. I like the lower first gear of the 200r4 over the 700, and I could reuse my driveshaft and no mounting modifications would be needed (I don't think). 3.06 just seems really tall. I've also heard that the change between 2nd and 3rd is bad. My father also has a 700r4 which he had built and he constantly has problems with it shifting at odd times but that could have been the builder's fault. None the less I appreciate the suggestion.

 

[Jr. Corvette]

Through many discussions with people I think I’m going to rebuild my TH400 and get the gear vendors unit. I might have to cut and do a bit of glass work but that’s really not bad considering the modifications to the crossmember needed for the T56 as well as the clutch master cylinder and shifter hole. It will give me 5 forward gears and an OD and it’s good for 1200hp. Master shift also work in conjuction with gear vendors so their paddle/ bump shift unit would work with it. The bump shift seems interesting but I don’t plan on doing that now if ever but it’s always nice to have options. With the tight foot wells I think I’ll leave the manual for a different car and honestly, trying to make that much horsepower work with a manual has it’s problems. If anyone’s interested on the install, I can post some pictures when the time comes.

 

[Black 03 Z06]

I really am not up on the state of the art automatics Jr. but the Turbo 400 was supposed to be a pretty stout piece in its day so with some modifications you should be able to make it do what you want. When you consider the massive horsepower some guys are running through Powerglides it is simply amazing.

Good luck with your swap.

 

[Brian Keery]

The easiest swap to get the overdrive feature that I've seen is going with the 200. Now as Turbozig mentioned, the consensus in my neighbourhood would be to go 700. But the 200 was literally a straight swap for my TH350 - didn't even mess with the driveshaft. Now I'm not looking for anywhere near your horsepower numbers......but then that opens up a whole other discussion on beefing up the rear end. I can tell you that going from 3200 rpm to 1700 rpm at 100km/hr was very enjoyable.

 

[Riley P]

Seems like you answered your question but I was going to go say to stick with the auto (the gear vendor's unit sounds like a great addition) but if you have a lot of time to modify your car, a 6 speed would be the way to go.

 

[Dub]

The turbo 400 trans has always been a very good, reliable transmission in my experiences at least/

 

[wildone909]

I have a 700r4 in mine but I don't have much more than 450hp... You must be going for a big block , nitrus or alcohol for 700hp. Great transmission. Modifying the cross member and driveshaft is a pain. The low first gear is nice but the gap between first and second is a little big. I have been running mine at an 1/8 mile track with no problems. Highway cruising was horrible at 2800rpm but is great now at 1800.

 

[Jr. Corvette]

Hey Guys. I did some more digging and found that the gear vendors unit isn’t all great. Some have had issues with bad customer service, many have brought up harsh shifts, and many with very short driveshafts have vibration issues. Now looking at a built 4L60E and here are my reasons.

-Although weaker in some aspects the 60E is about 100lbs lighter than it’s 80E counter parts and has a lower overdrive gear. I believe a lot of the weight of the 4L80E is also in the torque convertor which I would think slows down the engine a bit.

-Better overdrive over the 4L80

-I can get a TCI trans controller to simplify the transmission setup

-I can get it built locally to save on shipping and currency exchange

-Aftermarket 2.75 first and 1.57 second gives me the gears of a 200r4

I know I didn’t get any votes or opinions on it but those are my reasons. I’d love to here any final thoughts, suggestions or tips, or even some words of caution against the 4L60E. I haven’t added the supercharger yet and probably won’t for a while so I could either get a stronger trans or only put in so much boost. I think I’d be plenty happy with around 650 if I need to keep it down for the transmission to live. The car only weighs 3370 with a full tank and has 275 street tires and never drag radials so the tires should break before anything else does.

Thanks again for all the suggestions! I greatly appreciate them all.

 

[buckhorn76]

the rear end will be scrap metal before the trans lets go. and the trans won't last long either.

 

[Corvetteplus]

road course with big horsepower you want to add or have (700-800HP) , i would go with stock manual transmission (muncie), might be heavier than anything you've mentioned but without suspension and brakes upgrades you will not going any faster on road/race course. i would get offset trailing arm for bigger rear tires , front/rear swaybar, diff ratio (3.36 or 3.55), big brakes (willwood set) and if you have budget, coilover (ridetech) and rack & pinion. its about twice of the budget for t56 swap but what a race car you'd have... that is my own opinion...............have fun

 

[Rruuff Day]

Once again, the levels of member knowledge and the willingness to share that knowledge on this forum never fails to amaze and impress me.

 

[Jr. Corvette]

road course with big horsepower you want to add or have (700-800HP) , i would go with stock manual transmission (muncie), might be heavier than anything you've mentioned but without suspension and brakes upgrades you will not going any faster on road/race course. i would get offset trailing arm for bigger rear tires , front/rear swaybar, diff ratio (3.36 or 3.55), big brakes (willwood set) and if you have budget, coilover (ridetech) and rack & pinion. its about twice of the budget for t56 swap but what a race car you'd have... that is my own opinion...............have fun

Believe me, I probably would go with a manual if I had the money. However I could see with the tight footwells that shifting could get frustrating. I’ve also looked into transmission builds with those power levels and it starts to get expensive with hardened brazed gears.

Ironically, I’ve got Wilwoods with D8-6 up front and D8-4 in the rear with drilled and slotted rotors brakes very well. Just rebuilt the rear last winter with van steel offset trailing arms and heavy duty smart struts with HEIM joints. Upgraded my wheels to 18” foose wheels with 275 in the rear. Front and rear factory sway bar (gymkaha option which also includes stiffer springs). Been thinking of getting some coil overs for the front to lower it as I don’t want to go the sketchy way and chop the springs and it’d also give me some adjustability. Already have the 3.55 rear diff. Rack and pinion would be nice but it’s expensive and I rebuilt my steering box two winters ago and it’s very tight now and drives live a new car but hopefully one day. Thanks for all the suggestions though! It makes me very glad to hear that I’m on the right track!

Just a quick update from me, Jr.IndecisiveCorvette! I think I’ve decided. 4L80E with a USShift control unit (these things are amazing from what I’ve read)! I found a 4L80E in Calgary for $500 (haven’t bought it yet) and I’m thinking of building it myself and getting the parts from my transmission guy. It’ll be strong and with my TH400 I could spin my 275 tires at 1500 rpm with a 2500 stall and 2300-5800 cam. I’d say if my motor has enough juice out of this power range to kick the tires, what do I really need a lower gear for. Somebody on another forum did two dyno pulls, one with a 4L60E and then with the 80 and they had nearly identicle power curves. Somebody also did a 4L80E vs T56 dyno pull and the 4L80E was only 8hp and 30 torque lower. Not too bad for an auto.

All in all it will probably be best. I think I hated my TH400 because it wouldn’t kick down properly, 1 gear would shift at 5400 (should be 5800) and second would shift at 4500 (unless you held it). I think with the controllable shifts and the USShift unit (claims to give you as close to a manual feel as any controller) I’ll be very happy.

Sorry for my indecisiveness. I really appreciate all the advice. I will try post some pictures of the transmission and give an update come summer on the USShift unit.

 

[Black 03 Z06]

Whatever direction you take with this I wish you good luck. Can't wait to see the pics of the car rolling on down the road.

 

[Jr. Corvette]

Hey guys.

An update to this thread. I have made my decision. After looking into rebuild and parts cost of a 4L80E it was gonna be around the same or potentially even more for a 4 speed automatic than switching to the 6 speed manual. I found it hard to justify 1 extra gear and a lot of money for something I really didn’t want.

After about 4 months of searching on kijiji I made the drive out Revelstoke yesturday to picked up a T56 6 speed! I plan to rebuild it and slowly aquire parts to do the conversion next winter. Thanks everyone for helping me make the decision.

So happy to put that to rest.

 

[Black 03 Z06]

Another convert.