Tranny rebuilt 4l60e 1995 still with harsh 1-2 shift, help with springs?

95Noobie said:

Yes, I agree it is time to decide to live with it, sell the truck, or pour more money in at a new shop. 2 questions. If the corvette servo or the band clearance there is giving the harsh shift, would it not also shift harsh in 4th? I thought the band also applies in 4th. I was wondering if that would help us decide. My other gears shift nice.

Does it make sense to take my accumulator and just flip the piston to to a legs up piston and put the single spring on top?

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These are good questions...

1. The fourth gear apply circuit has a lot more accumulation and, by design, is much softer shifting than 2nd gear. As from the factory, the 3-4 upshift feed hole in the spacer plate is markedly smaller as well. So excessive band clearance won't have the same effect on the 3-4 upshift as it does on the 1-2. Again, this assumes everything is held 'equal' (i.e. no mods to the transmission in any way, baselining it from the factory)

2. You can try to flip the piston to see what sort of effect it has...Transgo has you do something similar to the 700R4 in all of their 700R4 shift kits...They use an in-board spring, have you put the piston on top of that spring, legs facing the spacer plate, then you install a larger spring between the up-turned piston and spacer plate.

I was looking on ebay and noted that the valve body for the 1995 was a one year only item. Now I'm wishing I had checked the stamped area on the valve body where they put the year to see if it said 95. Maybe the wrong valve body was used. This ebay ad near the bottom shows where they stamp the year.

rebuilt 1995 valve body

I guess all things to share with the tranny shop if we end up there.

NickTransmissions said:

These are good questions...

1. The fourth gear apply circuit has a lot more accumulation and, by design, is much softer shifting than 2nd gear. As from the factory, the 3-4 upshift feed hole in the spacer plate is markedly smaller as well. So excessive band clearance won't have the same effect on the 3-4 upshift as it does on the 1-2. Again, this assumes everything is held 'equal' (i.e. no mods to the transmission in any way, baselining it from the factory)

2. You can try to flip the piston to see what sort of effect it has...Transgo has you do something similar to the 700R4 in all of their 700R4 shift kits...They use an in-board spring, have you put the piston on top of that spring, legs facing the spacer plate, then you install a larger spring between the up-turned piston and spacer plate.

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So to help me understand, if I flip the piston so legs are up and put a single spring ABOVE the piston and against the plate, is there anything that goes UNDER the piston? I don't exactly understand which little channel the fluid goes through and whether it pushes on the underside of the piston or the top side or both. It would seem there would have to be a spring on the inside of the accumulator to keep the piston from bottoming out and what would then make it want to go back up against the spring that is now positioned above it? Would want to have what I need on hand before dropping the pan again.

I will try to get the spring you sent in a link a few posts back for above the piston although I have the 2 springs already on hand (the larger black one that fits in the piston) and the small yellow very firm one that goes in the smaller recessed hole in the bottom of the housing under the current piston.

95Noobie said:

So to help me understand, if I flip the piston so legs are up and put a single spring ABOVE the piston and against the plate, is there anything that goes UNDER the piston? I don't exactly understand which little channel the fluid goes through and whether it pushes on the underside of the piston or the top side or both. It would seem there would have to be a spring on the inside of the accumulator to keep the piston from bottoming out and what would then make it want to go back up against the spring that is now positioned above it? Would want to have what I need on hand before dropping the pan again.

I will try to get the spring you sent in a link a few posts back for above the piston although I have the 2 springs already on hand (the larger black one that fits in the piston) and the small yellow very firm one that goes in the smaller recessed hole in the bottom of the housing under the current piston.

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Here's what you need on hand for sure before doing any more work:

1. A first design 1-2 accumulator housing, new aluminum large hole accumulator piston
2. Sonnax 1-2 accumulator factory replacement spring and seal
3. Dial indicator w/base or short machinist rules

You can try different combinations of piston/spring arrangements but I'm not going to try predicting what difference they will make and whether or not you'll accomplish anything via experimentation simply because there are too many other variables that you either:

> unwilling to check due to lack of comfort/confidence you'll complete the work correctly (see my list a few posts above)
> unable to check due to lack of tooling, measuring aids, etc

And even if you install the correct piston and housing, you still may have a harsh 1-2 shift due to all the multitude of factors previously mentioned. Like I have previously advised, you must measure your servo travel!

Excessive travel is extremely hard on your band and you risk actually breaking it if the amount of travel is large enough.
Prioritize this task before doing anything else, other than acquiring a first design 1-2 housing.

Let me know if you're having trouble finding that first design 1-2 accumulator housing and I'll see what I can do to source one for you.

Yes, your directions are helpful and the priority of one step before another makes sense.

I guess the question was, when you had to replace the 1-2 accumulator in your customer's 1995 pickup to the proper accumulator, and put the piston legs up with the purple spring above it, was there a spring below the piston yes/no and if yes which one? Or is setup proper with only the single purple spring on top?

I appreciate the offer to help me source parts. I'm working on an exhaust leak, and somehow when they put the rear drive shaft in (or when I put it in last) I didn't notice much dripping but now it is dripping at the seal. The seal which was brand new before it went to the tranny shop now looks dented on one side. I will replace that and see if that solves the drip from the rear of the transfer case. Then I spotted a small leak from the transmission lines as they enter the tranny, that is new too. I guess the old lines don't like getting taken out and put back that many times. I will inspect to see if they have o rings behind the flares and if they need new O rings I'll source those and try to get that leak buttoned up.

meanwhile I'm checking ebay and checking local junk yard for what parts I might be able to come across.

The other day I passed an OBS Chevy that looked pretty nice but the custom license plate really resonated with me.. and made me smile. It said 'MONEYPIT'

If it were my truck I would start over with a stock 95 core and have a reputable shop rebuild it for you. There is no telling what all is wrong inside the trans you have! I’ve shipped trans across the continent to get the best builders work.

95Noobie said:

I guess the question was, when you had to replace the 1-2 accumulator in your customer's 1995 pickup to the proper accumulator, and put the piston legs up with the purple spring above it, was there a spring below the piston yes/no and if yes which one? Or is setup proper with only the single purple spring on top?

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Here's what it should look like when you have it together.

NickTransmissions said:

Here's what it should look like when you have it together.

You must be registered for see images attach

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So from the picture it looks like the piston has no spring under it, it bottoms out in the housing and the single spring goes above it. Thanks, I couldn't understand if it rested on the bottom of the housing how it would move up (while I could understand how the spring would prevent it from moving all the way to the top) and then if it was in the up position how it would get back to the bottom again.

And Sean Buick you are correct that my desire to drop the pan again is also to satisfy my curiousity if the valve body even IS a '95 or not. I agree that getting a rebuilt 95 valve and a good tranny shop to check install tolerances is the next step.

Nick is a top notch builder as you can tell by his replies, also he has the best videos out there. You should watch a few and maybe you would be more comfortable with pulling the valve body and drilling the separator plate as he suggested. You can use drill bits as pin gauges to roughly measure the current holes if you don't have any better tools for the job. A caliper would make it easier and would be accurate enough.

Is there is any chance the valve body might have had a transgo shift kit installed? If so, there is one other thing that might be worth a look if you take it apart, number 2 on the top right of page 6 of transgo SK4l60e instructions. The spring they put in the 1-2 accum bushing could be non-stock. A heavier spring will shift harder as it will increase the pressure so flow to the 1-2 accumulator. If the two builders didn't take the VB apart they may not have known if this was changed. It would be more noticable at heavier throttle.

One other item from your comments, do you think the builder that talked about blocking the accumulator might have been talking about the 3-4 rather then the 1-2? That would make more sense and most would recommend blocking the 3-4 accumultor. If you take it apart you should consider it while you're in there.

Vic327 said:

Nick is a top notch builder as you can tell by his replies, also he has the best videos out there. You should watch a few and maybe you would be more comfortable with pulling the valve body and drilling the separator plate as he suggested. You can use drill bits as pin gauges to roughly measure the current holes if you don't have any better tools for the job. A caliper would make it easier and would be accurate enough.

Is there is any chance the valve body might have had a transgo shift kit installed? If so, there is one other thing that might be worth a look if you take it apart, number 2 on the top right of page 6 of transgo SK4l60e instructions. The spring they put in the 1-2 accum bushing could be non-stock. A heavier spring will shift harder as it will increase the pressure so flow to the 1-2 accumulator. If the two builders didn't take the VB apart they may not have known if this was changed. It would be more noticable at heavier throttle.

One other item from your comments, do you think the builder that talked about blocking the accumulator might have been talking about the 3-4 rather then the 1-2? That would make more sense and most would recommend blocking the 3-4 accumultor. If you take it apart you should consider it while you're in there.

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Thanks Vic!
Yes, Nick has been helpful and clearly understands these things down to the finest detail. He shared a picture but I can't still get one detail straight. Maybe you can help? When I go back in to put the piston upside down and legs up like in his picture, I get it that the spring then goes on top of the piston against the plate. But does a spring go UNDER the piston too? I can't see that in his picture. It would seem like there would have to be something under the piston to help move it up if it wants to go all the way down as I'm not aware of any fluid pressure that would exert UNDER the piston to push it back up. Once I can understand that I can drop the pan and flip the piston.

As to having a shift kit in the valve body, I can ask my last tranny builder.. I would say no, I would think he would have seen that when going through it all, but I can check.

I'm pretty confident the 3-4 accumulator is untouched. The only change was to take the 1-2 accumulator which came to me with 3 springs inside and the piston setup that the later model trucks use and I switched it to a sonnax pistonless thinking the hard shift was due to wear around the pin. When I took the original 1-2 accumulator out there didn't seem to be any wear or slop around the piston in its housing or in the piston hole so i wasn't sure it would fix anything to make it pistonless and sure enough it didn't.

That means that if it was designed to have the piston upside down with single spring on top i should at least try that. But as Nick said, several other things in the valve body could be wrong and the servo clearance needs to be checked as well.