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Hello,

I'm pulling out the L03 and 700R4 combo in my 91' wagon to use in another project. The transmission shifts very slowly and softly, nice for grandpa's cruiser, but I dislike it. Besides, I feel like the soft shifts are going to kill the trans sooner. I'd like to firm up the shifts a bit and I'm thinking a "corvette servo", like what's in an LT1 car, might do the trick. Thoughts?
 

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Just for reference, the “Corvette” servo only increases clamping load in second gear. And, if you install it without adjusting the shift feed hole orifice, it’ll actually shift slower than the servo piston that’s in there.

I have no experience with 700R4 shift modifications. The advice above is useful.
 

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street strip i used this kit. he calls or email you for details of your particular objective. I liked he had cryoed accumlator housing and pistons. I had a complete rebuild done locally and used his shift kit. moderate to firm shifts depending how hard im on it for every gear. I also used big 4th apply
 

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Dana's "heavy duty" kit will be fine. the bigger 4th servo is only necessary if you are making WOT 3-4 shifts often or heavy towing. do not get caught up in gimmick servos, the vette servo is FINE for 95% of builds. Dana offers new Transgo separator plates that he will pre-drill to your tastes. I would not recommend going overboard here. VERY easy to make 1-2 shift to firm, i usually leave it stock but no bigger than .070"ish range unless using a small diameter torque converter. it is very hard to make 4th shift to firm, i block the 4th accumulator feed and discard the piston and spring, Dana does the same thing in his kits.

on that note Dana can be hard to get ahold of, just be patient i believe he is in his mid-70s now! best to call him on the late afternoons or evenings, he is a night owl. weekends are fine too....
 

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VERY easy to make 1-2 shift to firm, i usually leave it stock but no bigger than .070"ish range unless using a small diameter torque converter.
Agreed on this. One of my recent builds (as of fall 2022) had a Sonnax HP-4L60E-01 shift kit, #553 truck servo (vehicle was a 97 C1500 5.7L 2WD), wide band, .093 hole for 1-2 shift and it is too firm at light throttle. It's fine at other throttle positions.

EDIT - I know this isn't fully relevant to OP but if someone searches and finds this thread, it'd be useful to have for anyone building a 4L60E.
 

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.093" is huge, I would not use Transgo shift hole recommendations, they are WAY off. Either too light or too firm from my experience.
Sonnax recommends .093" for a number of the feed holes including the 1-2 shift. I agree, it makes it too firm at light throttle.
 

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Not sure if you have done anything yet, but you should go on YouTube and check out Precision Transmissions and any of the 700r4 videos he has done. This guy and his son breakdown transmissions on video in a clear and thorough way. They will also give you tons of info on what the weak points and parts to help certain things on the transmissions. Plus you'll have every step to do it on video.
 

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Not sure if you have done anything yet, but you should go on YouTube and check out Precision Transmissions and any of the 700r4 videos he has done. This guy and his son breakdown transmissions on video in a clear and thorough way. They will also give you tons of info on what the weak points and parts to help certain things on the transmissions. Plus you'll have every step to do it on video.
for starters i don't think precision transmission's has EVER done a build video. 2nd, a lot of his advice is outdated and just plain BAD. Z-pack clutches? the stock borgwarner HE clutches work fine. Stacking pistons in the 4th accumulator like he shows in all his videos actually KILLS lube to the rear gear train. Welding the TCC valve from moving? Not only is this dumb, but all you need to do is flip the inboard valve 180* and it turns the TCC into an on/off arrangement. Sillicone on the pump halves? I could go on and on here. The guy is a hack as far as i'm concerned.
 

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for starters i don't think precision transmission's has EVER done a build video. 2nd, a lot of his advice is outdated and just plain BAD. Z-pack clutches? the stock borgwarner HE clutches work fine. Stacking pistons in the 4th accumulator like he shows in all his videos actually KILLS lube to the rear gear train. Welding the TCC valve from moving? Not only is this dumb, but all you need to do is flip the inboard valve 180* and it turns the TCC into an on/off arrangement. Sillicone on the pump halves? I could go on and on here. The guy is a hack as far as i'm concerned.
If he takes it all apart, then could you not put it back in reverse order? That's not complicated, especially if you are confident enough to take it apart to begin with. I'm no transmission guy myself so maybe you are a transmission GOD but I haven't heard bad things about Z-Packs. The dude also explains plenty of things in detail and gives you tips worth learning. The trans is outdated so how is his advice outdated? He has been around for plenty of years and has plenty of transmissions under his belt from race application to off road. To each their own and take all advice with a grain of salt. Apparently Tayto, you need to put your own video's up. Not many guys are willing to put their work on video for the world to criticize.
 

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I would agree with @tayto , take Precision's recommendations with a grain of salt. He obsesses over some things that don't matter (like the feedhole shape of the reverse drum), and blocking the TCC regulator valve in the full open position is hackery at its finest, whereas the Sonnax TCC regulator valve permanently solves the problem and lets you control lockup feel in the PCM. And just like engine assembly and disassembly, there is vastly different knowledge there. Personally, I can't stand that he disassembles the geartrain with the transmission laying on its side. Ugh.

As far as shift quality, you need to address all of these simultaneously: line pressure (pump, EPC, AFL, pressure regulator, boost valve), shift hole orifice sizes, accumulator spring stack, and accumulator valve spring/shim. Any fool who takes apart a 4L60E with a burned-up 3-4 clutchpack and just replaces geartrain parts (or maybe throws out the 3-4 load release springs) is a hack.
 

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Dana's "heavy duty" kit will be fine. the bigger 4th servo is only necessary if you are making WOT 3-4 shifts often or heavy towing. do not get caught up in gimmick servos, the vette servo is FINE for 95% of builds. Dana offers new Transgo separator plates that he will pre-drill to your tastes. I would not recommend going overboard here. VERY easy to make 1-2 shift to firm, i usually leave it stock but no bigger than .070"ish range unless using a small diameter torque converter. it is very hard to make 4th shift to firm, i block the 4th accumulator feed and discard the piston and spring, Dana does the same thing in his kits.

on that note Dana can be hard to get ahold of, just be patient i believe he is in his mid-70s now! best to call him on the late afternoons or evenings, he is a night owl. weekends are fine too....
If you forget to put in the restrictor plug on the back side of 4th gear apply piston, 4th gear will be sledgehammer like :)
 
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