A Question, and a long story.

The Question: I have a 1993 with that lovely one-year-only version of the 4L60 transmission (5 pin, no "e", extra check ball). I had a new 3.55 rear end put in, replacing my 2.59, and put an electronic speedo compensator. The mechanic is telling me that the car is shifting too soon. When I delivered the car to the first mechanic, it was shifting fine (why there's another mechanic is part of the "long story"). I had a Trans-go jr. shift kit and .472 TV bost valve installed. According to the mechanic doing the transmission work, the car was shifting too soon/early when he received it-- and he's at a complete loss as to what's up (and 3 people have been at the TV cable, so I doubt thats the issue).

Any idea's from our hydraulic transmission folks here?

Long story...

Brought my car to an old-timer to do an Opti, larger radiator, cowl brace, frame braces and a new 3.55 rear end (old was 2.59). He got all the work done, heard it run over the phone--all is well. I wanted to top it off with a shift kit, but he felt more comfortable having a fellow mechanic--his transmission guy-- do that job. So then his wife has a stroke, and then he dies.

The kids call me, they know dad was working on my car, but they don't know where the car is.

No seriously, this happened.

Found the car, thanks to another Vette owner who saw it in the shop he was having work done. And as stated above, this mechanic says the car was shifting too soon when he got it from the dead guy. He's tinkered with it, and brought other guys in to tinker with it--they can't figure it out. If this mechanic is right, then it would seem the rear end change is affecting the transmissions shift points--but the 93 is NOT an electronic trans. I did a lot of reading here before I embarked on this, and I've fund nothing that says the rear end gear change affects automatic shift points. He wants to replace the valve body now, but the car has less than 60k on it.

And, between vacations, winter storage (with the dead guy--nice of him), strokes, being polite, death, and mystery shifts--I've literally not seen my car in 8 months. I also found a post just yesterday saying the 93's don't like trans-go kits. A post from 2007 that never showed up on my pervious searches--everyone had good reviews for trans-go.

2020 was actually a better year. ;-)

Ronn

 

Sounds like the governor needs tweaked.

 

Ihatebarkingdogs—

wow, that’s one of the best responses I’ve ever received here. I must have 1/2 dozen threads I’ve started or contributed to regarding switching the rear end on my AUTOMATIC C4, lots of people discussing speedo and odometer error, and not a word about a governer. Though in all fairness, my questions/comments focused on the rear end.

at any rate— thanks for the really useful response.

I believe 3.54/5 rear ends are standard on many GM cars. I know not just any old 700R/4L60 will fit a vette, but my understanding these are mostly attachment/coupling differences. Would a govener from another GM vehicular (sharing a 4L60 trans) have a govener that would work in the vette? Or are there internal differences Bergen give ERS in various 4L60 application?

thanks again

Ronn

 

The governors are mostly the same in GM cars. Even turbo 350s and 400s. The difference is the weight/spring combination. Different cars have different set ups. In the case of your Vette it will be trial and error to get it shifting exactly as you need. I think it took me 5 tries to get mine perfect. That was a lot of years ago so I do not recall exactly what I ended up with.

 

Yes but you didn't go far enough. The gear twist is opposite on the 400. Can't just pop a 400 into a 350.

 

You will likely have to live with some of it due to gear ratios. With.your 3.54 axle and a 3.06 first gear 17 mph is 2500 rpm transmission typically shifts undet 2k. 2nd gear is 1.68 and 2500 rpm is around 34. The governor sets the max engine RPM will reach before it will shift. 5-5.5k is in the ball park. You could play with the valve body changing springs on the shift valves trying to move shift. IDK that you want to change all off them. Your going to notice the engine winding up. Changing the governor will alter all the shifts. Delaying shift will increase rpm when it occurs.

 

I did not know that. Good catch. Never owned a T350. I have had 400s and 700s.

 

You need to go back and read IHBD's post, especially the last sentence. What does 5-5500 RPM have to do with adjusting governor weights to adapt to a new gear ratio and needed ground speed shift? This is not the first time you have thrown a handful at the wall hoping some will stick when discussing these trans.

 

I spent a lot of time trying to dial in the shift points for my (at the time) street/strip 700r4. Changing the shift points for good street driving affected wot shift points and vice versa. I bought 2 shift kits and mixed and matched weights and springs and even took to grinding the weights to try to get things dialed in. Finally, changed to a 4l60e and shift points are easily adjusted part throttle and wot with the touch of laptop keys.

 

Great information from everyone--thank you!

If you'll suffer another newbie 4L60 question...

At this point, with a stock motor, the factory shift points are fine with me. I quick perusal of online information reveals mostly efforts to change the stock shift points higher; i.e. they are starting from stock and not from scratch (or 40% off like me). Am I understanding correctly that 700R4/4L60 vets never came with 3.54 rear ends (I beleive maules did), and a governor from, say an F Body with a 3.5 rear end, will NOT give me a closer starting point? Likewise, is there a vendor that could set up a sonomax (or the likes) governor with weights to get me to stock shift points?

Even more pointedly, is there anyopne from say this thread https://www.corvetteforum.com/forums...pm-survey.html share where they ended up weiht/spring wise with their 3.54 rear end?

Thanks-- these C4's are puzzels sometimes...

Ronn