Swapping 700r4 to 4L60 (or possibly 4L80)

[usar17]

Swapping 700r4 to 4L60e (or possibly 4L80e)

Here is this years long term project. Last year I swapped out my carb 305 for a TBI 350. Now that its all tuned and running perfect I'm in love. I had to cut the crap out if my torque converter inspection cover tho to make it fit the new engine. And it still isn't right.

Currently my transmission is the only thing original on my truck. Idk if its ever been rebuilt or what. Its backed by a NP208 transfer case. Currently I'm getting not rough but very noticeable shifts until the transmissions warm. I changed the fluid and filter twice (once when I got the truck 3 years ago and last year when I replaced the tcc solenoid). The fluid gets dark quick. The TV cable is also getting a little stiff to pull. But besides that she's good. I get surprisingly good gas milage and accelerstion isn't an issue. 4.10 gears with 32" tires. I don't do heavy loads or pulls often and only occasional mud slinging.

So my thoughts are newer model transmission to match the motor, keep them both working together off the ecm to better the effrciency. Or is this not correct? I know newer isn't always better lol.

Currently the GMT400 series is in large abundance at my local u-pull-it lot. I shouldn't have any issue pulling a tranny. I've never opened up a transmission and I'm curious to rebuild one. Am I insane for trying Haha? My main question to you educated individuals (Haha) is what changes will I need to make to my setup to swap in a 90s tranny? Im aware of electronics and ECM. What about the transfer case side of things? Id prefer a direct swap in which is why I'm leaning towards a 4L60e over the 80. Unless the bolt pattern on the back of the 60 is also gonna make me have to replace everything.

Thanks!

 

[HotRodPC]

There really is no big benefit IMO in swapping from a 700r4 to a 4L60-E unless you just want it to be electronic controlled. If you find you an 88-92(3) 700r4, you've pretty much got the best core to build a 700r4 with and pretty equal to the 4L60-E in strength. Now the 4L80-E is for sure a step up in strength, so if you're going thru the motions, go for the 4L80-E otherwise just find you a 88-92 700r4 core and have it built.

 

[usar17]

But with the 4L80e wouldn't I need to change my transfer case? Or does it have the same 4 bolt pattern as the 60?

 

[HotRodPC]

yes, you will need a different input spline and adapter for the Tcase to go 4L80-E. And you'll need the controller for the -E trans too. IIRC, the same adapter on Th400/NP208 also fits the 4L80-E, so if you found a NP208 off a Th400 trans, chances are it will fit a 4L80-E too. I know the spline count will be the same at 32. Th350, 700r4 and 4L60-E are all 27 spline.

If you're just light to mild on your truck, you might just stick with the 700r4, but try to find a better core as in the 88-92. There were updates every year for the 700r4 making improvements every year. The more critical changes are all made by 88.

 

[usar17]

Ya I wanted to stick with the 700/4L60 since I'm more mild with my truck. Just wasn't sure if letting the ECM control the tranny would make a difference. I wouldn't mind eliminating the TV cable.

 

[HotRodPC]

That is about the only advantage to the 4L60-E over the 700r4. And that the ECM also controls lock up of the Torque Converter. But, in TBI models, like 87 trucks and 87 - 91 Burbs and Blazers that are also TBI, the ECM controls the Lock up TCC also, but that's all the ECM controls in a 87-91. They still have a governor and TV Cable.

Also keep in mind, even if you got 4L60-E, then you need to adapt a TPS (Throttle Position Sensor) to your carb or gas pedal linkage which takes the place of the TV Cable. So no matter how you slice it, you're going to have something connected to your linkage, either a cable or a sensor.

But yes, a 4L60-E will bolt right in where your 700r4 does, then you also have to convert to an Electronic Speedometer which is easily done by getting a speedo out of 89-91 Blazer or Burb. (I think that is the years, we'd want to make sure with Retro to be certain).

 

[usar17]

I have a TBI motor already. So sensors aren't an issue. My ECM currently controls my 700r4. I rewired it for that. So a 88-91 would plug right in. As for speedo I get my signal mechanically from the transfer case. I would assume a 4L60-E would just require me to run a few more wires between the tranny and ECM.

 

[HotRodPC]

True, you'll need to get a Tcase with the reluctor wheel instead of the mechanical gears on the output shaft for the speedo. But again, check with Retro. I know some of those speedo's have converters for VSS, just not sure it's compatible with 4L60-E. You might not have a choice but to go electric speedo.

 

[usar17]

As in using the signal from my cruise control module Haha

 

[HotRodPC]

As in using the signal from my cruise control module Haha

That's what I'm talking about, and not sure that will work for a 4L60-E or not. That's the converter I'm referring to. I'm thinking NO, it needs to get it from the VSS directly.

 

[usar17]

Has there been any proven increase I'm efficiency between the 4L60 and the 4L60-E?

 

[HotRodPC]

Not that I can recall. You know 700r4/4L60 are the same thing right? GM renamed transmisisons to know the speeds, type of install and strength. So a 700r4 became the 4L60, 4 speed, Longitudinal Install, 60 for the strength rating. Th400 became 3L80. 3 speed, Longituidinal Install, 80 for the strength rating. Hence a 4L80-E being a Th400 with an OD and the -E mean electronically (computer) controlled. So a 4T60-E would be a 4 speed, Transverse Install (Front Wheel Drive) 60 strength and the E of course. I think it was the Th125C that became the 3T40. A FWD 4 cyl transmission. So it's easy to figure out that a 4L60-E and a 4T60-E are very similar in strngth but one is for Rear Wheel Drive, other is for FWD.

 

[usar17]

Yes I know the 700r4 was renamed to the 4L60. Was just curious about when they went from TV and fluid controlled to electrical if it improved anything

 

[HotRodPC]

Yes I know the 700r4 was renamed to the 4L60. Was just curious about when they went from TV and fluid controlled to electrical if it improved anything

That was 93 when they went to 4L60-E, but there were a few straggler models that stayed 700r4. It's rare to see a 93 700r4, but they do exist but some say the 93's just got the leftover 92's so you won't find a 93 700r4 and that's possible too. But by 94, there were no 700r4's in production vehicles.

No, as far as strength, it didn't improve anything. It may be possible some operation features are better since the ECM get's to control the transmission too, but I'm not so sure myself if it's better or not. Same as anything. Pros and Cons either way.

 

[usar17]

I figure strenghth isn't changed BC its still the same weight ratings and components for the most part. Just was curious if the ecm interaction helped with fuel economy.

How crazy is it to rebuild one? Am I a fool to try and do this as a novice?