My transmission (TH-700R-4) needs to be replaced.

I was wondering if anyone has tried using a TH350 or TH400 on a stock 5.7L TPI motor.

I know the 700R-4 has the lower first gear and overdrive. I am not sure how the stock 5.7L will work without the lower first gear and an overdrive.

Has anyone tried using a TH350 or TH400 on a stock 5.7L Tune Port Injection motor? And if so how did it work. Would it be slower off the line, would I lose top end speed? Any information would be helpful.

 

You'd probably end up faster with a TH350/400 on a TPI engine (quarter mile performance).. An L98 has so much torque available down low, there is little need for such a low first gear. I don't know whether its worth it to sacrifice the overdrive and the lockup converter (and their associated gas mileage benefits), but that all depends on what you're using the car for...

 

Easy swap, make sure you buy a torque arm kit. You will also dislike driving on highways.

 

why does everyone say this???

there were how many years without overdrive that it didnt effect the car or driving on the highway..LOL...i understand that it will probably kill the poor guys gas mileage but he obviously knows that ....

the torque arm kit is a good idea but also check out this set up here

this one is for the th350

http://www.bulkpart.com/Merchant2/me...y_Code=Teckpak

this one is for the th400

http://www.bulkpart.com/Merchant2/me...Category_Code=

these will let you keep the factory 700r4 tailshaft from your transmission and install it onto a th350 or a th400 and then you dont have to mess with all the torque arm problems or speedo problems or anything else....

 

what about computer issues ?

 

I believe that adapter block is unnecessary, as I do not have one, and If I did have one, the transmission would be too long and the driveshaft would need to be shortened.

You will still need a torque arm kit.

I hate driving mine on the highway, so I thought that I would tell you that. Sorry if it ruined your day.

The output shaft should be compatible as-is and if it isnt, you can always use the other yolk. Therefore, I beleve that whole kit is unnecessary. Maybe I have a long tailhousing? Pretty sure I don't but I can check.

 

Ok, thanks for the pointers.

 

1. with this kit you dont need a torque arm kit at all you use a 700r4 tailshaft and tail housing with the factory torque arm mount on it ...

2. it didnt ruin my day never said it did i just think its silly when (not you ) but alot of other guys on here will tell people they arent going to like driving on the highway without overdrive ...LOL

3. the output shaft from a 700r4 is installed into the th350 or the th400 depending which kit you buy and then the tail shaft from the 700r4 is bolted to the adapter block giving it the proper length to not have to deal with speedometer issues or driveshaft length issues.

we have used this kit before and it works flawlessly without any problems what so ever.....

heres a couple pics of one installed on a th350 in my brothers transmission we used in his camaro...





heres a thread about the whole situation also ...https://www.thirdgen.org/techbb2/sho...5&pagenumber=1

 

Wow, mine is set up entirely differently, but accomplishes the same thing. I'll snap a few pictures while im swapping motors this weekend.

The only thing I might worry about with that setup is the integrity of the stock torque arm mount, as the bolts are quite a bit longer now. I already stripped the 4 tailhousing bolts without the spacer, but this is with a transbrake on a 10 second car.

 

Wow, mine is set up entirely differently, but accomplishes the same thing. I'll snap a few pictures while im swapping motors this weekend.

The only thing I might worry about with that setup is the integrity of the stock torque arm mount, as the bolts are quite a bit longer now. I already stripped the 4 tailhousing bolts without the spacer, but this is with a transbrake on a 10 second car.

 

I installed a TH350-C in my 89 IROC-Z with a L98. It works great, first gear is a blast (even with the stock 2.77 gears). The TH350-C model does have a lockup converter, but less choices as far as shift kits (no manual valve bodies). Yes it does make my gas milage on the freeway totally crappy (even with lockup) but that was my choice. The TH350 I used came out of an 86 truck and had the long tailshaft so I was able to re-use the stock driveshaft. I also did the torque arm conversion kit (Hurst). Be aware that there are three different styles of torque arm brackets and this can possibly affect these conversion kits. The bracket I had happened to be the wrong one so I had to do some drilling to get the conversion kit to bolt up properly. I tried to use dipstick tubes for "TH350's" but I could not get them to fit properly. I ended up going with the Lokar bendable dipstick tube. I also used the Lokar kickdown cable. I attached the vaccum connection to a vaccum line right in front of the distributor cap (with a vaccum T). I also had to bend the cooling lines to fit, be sure not to bend them too much. I tried to re-use the stock 700R4 crossmember (and after drilling it did bolt up), but looked too flimsy to me. Since I'm hard on the car, constant throttle for long periods of time, I got a Spohn TH350 crossmember (much stronger, also overpriced IMO). The best budget way to do the swap is find a 82 or 83 F-Body 200C donor car. Those crossmembers will work fine.

If you want OD for the freeway (aka good gas milage) then go with the TH400.

 

there are many different ways to accomplish the same results on a thirdgen with the torque arm mount ...you can do as we did or you can use a bracket kit either one is going to work depending upon which transmission you use and tailshaft length you have on which way you will want to go