hello guys, I have a question about the interchangablility of transmissions for GM in the 90's. I'll try to give you the basics of what i've done, and what my situation is, then tell you all the specifics of my set up. I have a 49 Studebaker pickup. We took the entire drivetrain from a chevy pickup and put it into the stude. Now everything works good, but the tranny has some issues. all parts are from a 1990 Chevy 1500 Silverado pickup, 2wd. 5.7L 350ci. V-8 TBI, (only mods: headers, aftermarket air cleaner, valve covers) 700R4 Transmission (lokar style top mount shifter, Speedo gears changed for cable driven speedometor, electronic pulse sensor for ECM) Modified S-10 Driveshaft and Stock rear differential OEM radiator/trans cooler Aftermarker wiring harness for engine/ trans/ ECM We DID NOT connect the Neutral safety switch wires or TCC lockup to the ECM the 700r4 does the following: Leaks tranny fluid, not sure from where? But a good bit. We put brand new fluid, new pan and gasket, new filter, and added lucas treament to it. Also the transmission has a hard time shifting. The shifts are sometimes hard, sometimes higher RPM then it should be, or wont shift at all. when it does shift we need to use the accelorator very slow and steady or feather it. We got a new TV cable and we think its adjusted properly. Since the new cable and everything we've done its been working better but not right. Plus we still have the leaking. Now im under the impression that it will probably cost me(depending on the extent of damage to my tranny) the same or more to rebuild this tranmission than it would to buy a rebuilt one that has upgraded parts, and bulletin specs upgraded. Having said all that i'm looking for my best option moving forward. 1: rebuild this one 2: Buy a rebuilt one 3: Get a different transmission. The last thing is what i really am in need of help with from you guys. I want to know what other transmissions out there will bolt up to my setup and work!!! I'm open to ANYTHING that will function. Older, newer, different make/model, automatic or manual!!! Hopefully you guys will be able to help with my options that will bolt on, match up, and function properly if option 1 or 2, isnt available. Thanks!
depending on how much money you have and how much you want to screw with it you can add any trans you want. 350 400 2004r 700r4 4spd 5 spd 6 spd sticks also. its the 350 ci engine that has been used for a long time and about every platform gm built that makes it so good for this. my money is with a bow tie 700r4 only after you find out what is wrong with yours. take to good trans shop and get the cost of fixing yours and setting it up with the pressure gauge. make the call then.
"We DID NOT connect the Neutral safety switch wires or TCC lockup to the ECM" You DID hook up the TCC to lock-up in 3rd and 4th......if not that could be some of your erratic shift problems.
If it has been driven for a while with the tcc disabled the planetaries are probably burned up. The tcc system has to be functioning in order to get full cooler flow. Return oil from trans cooler is used to lube the planetary gear train.
Oil leakage could be from oil coming out of the vent due to high fluid temperature due to the non working tcc.
sorry if i'm a little fuzzy on the details. All this was done around October and its been in the garage since. I know i bought an aftermarket wiring harness for the TBI system with the oem ecm. On the wiring harness there was those 2 wires. One single wire each for TCC and NSS. With the top mount shifter we needed to figure a way to wire up the neutral safety switch and it being a hot rod we just said it will be fine without it for the time being. The TCC wire. we werent sure what wire from the tranny came and connected to that? Now i'm not saying we did NO harm to the transmission, but when we bought the donor truck the guy told us he did have problems with the transmission not shifting, he said he had reverse and first. Come to find out not only did he have a really bad (stuck) TV cable, but the cable was hooked up wrong at the Throttle body. i have no idea how long he drove it or how hard he drove it like that. Since its been in my truck its seen about 30 min. of road time total over mutliple short trips for testing. Since then we bought a B&M tv cable, hooked it up, and adjusted it according to many videos i watched for demo purposes. After we did that, we took it around the block a few times to test it. we got it to go through the gears. and we even had it up to 45 mph in 3rd. The more it cycled through the gears the better it was the each time. But it still didnt seems right and it seemed like the engine was getting a workout. Also then is when the leaking fluid worsened. I'm thinking that rebuild is probably the best, i just want to make sure whatever price that is its worth it. some rebuilds you can buy are upgraded with high performance or heavy duty parts to fix common problems that these transmissions encountered. i'd want that level of rebuild is what i'm saying i guess.
and just to clarify, the leaking is as the car sits. when pulling into garage we see a small spot trail, but come in the next day to a puddle.
A long tailshaft TH350 should bolt in, and get you driving, for a reasonable cost. A short one will fit too, but requires you to get a longer driveshaft made. The transmission crossmember would have to be moved forward a bit. No overdrive....so if your rearend gearing is not right, you'll probably not like driving it on the highway too much. A 200-4R will also fit with a longer driveshaft, and possibly moving the crossmember, it's overdrive, and will probably cost as much as a 700 to get built.
I'd go ahead and rebuild it. Kevlar clutches, and a Corvette servo are about all I do. Harsh shifts get old after the first week.
700R4 TV cables have a special adjuster at the throttle and the arm on the throttle shaft is a specific calibrated length, the position of the valve inside the transmission case is what controls all the functions of the transmission, not just kick down like older style autos. If the cable is adjusted wrong you pretty much destroy the transmission instantly the first time you drive it and there is no quick fix. Sorry to say that seems to be the case from what the previous owner did. The torque convertor clutch will have no effect on what you're describing, it just locks up the convertor to improve fuel economy by eliminating the slippage that's inherent of using a fluid coupler to transfer torque.
If you run with the converter unlocked in 4th (or 3rd and 4th, on some models), it will run a little hotter than with it locked. That's about it.
I'd talk to Steve Weik about it. Weiky, isn't cheap but he sure knows his tranny shit. Good luck with it. Edit: 717-866 -5809 Steve's Trans
Rather then read all the responses let me give you my thoughts then if they over lap you have good reason to believe that either I or the other responders is on the right track. More likely the other responders. First off a leak transmission is doesn't mean a rebuild is necessary, find the leak and fix it. Likely places for the tranny to leak are the pan gasket, tail shaft seal, front seal, dip stick tube, TV cable, cooling lines. Next weird shifts on a 700R are likely caused by poorly adjusted TV cable, sticking or broker governor (under that little derby hat looking thing held in by a bale clip), band out of adjustment, torque converter not properly seated. Sometimes but rare bad lockup switch. As far as transmissions for your 90s GM any GM automatic will work, 200R, Turbo 350/375, turbo 400, power slip. You can also go with a 4L60 or 80 series tranny if you are willing to drop the coin and jump through the hoops but I wouldn't bother. I have run the 700R and prefer the 200R over the 700r if I think I need an OD. My personal preference in automatics are the turbo 350 or turbo 400. That is just because I don't care for automatic OD, it is a quirk and should not have any bearing on your decision.
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