HighMileageC4

I rebuilt my 4l60e in my 96 vette last winter. It shifts great at part and wot. Very firm. It has a modified trango shift kit from probuilt trans.

Has all of the common upgrades and is equivalent to a level 5 from the top vendors.

My irritating problem is after trans warms up past 180, it has a small delay when giving gas from a dead stop. You can feel a small bump after giving gas pedal, almost like it takes a certain rpm to get it to move and you feel something engage. It does not do this cold, only when fully warmed. It has gotten more noticeable now that it is warmer here in chicago.

It did this before the rebuild, and still does this. Given shift quality isgreat, this has me stumped.

I changed converter from tci to a yank3200 after the build. Yank says it must be trans, not converter.

Also seems to happen when going from reverse to forward, but only when warm.

Any advice? Maybe a worn valve in valvebody?

I checked 1-2 accumulator (transgo setup) and seals are good. Also checked fwd accumulator which has sonnax billet piston and that looked good.

Gearstar Performance

It is a possibility that it could be a worn valve body. Particularly looking at the forward and reverse abuse valves. Sonnax has a repair kit for these. Here is a link: http://www.sonnax.com/product-lines/...ion/parts/1251

mrvedit

That sounds like good advice from Gearstar. Some Sonnax repair kits require an expensive reamer, but NOT this one. Each valve kit is only $13; you need two:

http://www.transmissionpartsusa.com/...-07775435k.htm

If that doesn't solve your problems, you might consider a rebuilt or a more recent model used valve body. If it comes to that, I can help you review what is available on ebay on the day you are looking. Figure on $100 to $170.

Dynamic396

Does it feel like it's going from a neutral condition and then engaging into forward when you give it throttle? Or does it feel like it's in a higher gear (say, 2nd...) and then dropping down into first when you give it throttle?

Does it do the same thing in manual low?

Have you checked you line pressure at a hot idle in "OD" range, 1st gear?

HighMileageC4

When I rebuilt the trans I put the Sonnax reverse abuse valve in it. I did not replace the forward abuse valve. All solenoid are new GM. I put the sonnax HD 2-3 valve also.

The band release check ball is plugged on the plate and check ball left out. I believe this maximizes oil to the 3-4 clutches during 2-3 shift.

It feels like a slight neutral condition and it then bumps into forward. Its slight. I either feather the gas pedal or brake and lightly give gas. If the rpms climb to about 1200 it engages. It does not feel like its trying to start from a higher gear.

It does it in manual low, slightly less but its still there.

I have not checked pressure, hope its not the pump, but as
I said the shift quality is very firm on all shifts. 4th is less firm, but I think 4l60e's are supposed to be like this. It shifts like a sledgehammer, progressively firmer with throttle.

Son ax is not really clear in their descriptions that the forward abuse valve would address this, but this would be the best case scenario. There are 7-8k miles on this rebuild.

flowride

Glad to have found this thread. I have a 1998 Camaro Z28 Convertible, bone stock, that is doing the same damn thing! I've taken it to two different mechanics and expressed my concern, but they both said I was crazy. Mine also hard shifts sometimes when this happens-usually from 1st to 2nd gear. Part or WOT? No problems whatsoever. It's very frustrating because while father time and $#!TTY SoCal roads beat my car, I don't.

A quick question as well: if it comes down to having to replace the transmission completely, would it be just about the same price to convert the car to a manual? Sorry guys, but I'm tech stupid and just asking.

mrvedit

I have noticed that line pressure drops slightly as the trans warms up; line pressure also tends to be lowest at idle and increases a bit as you rev the engine. Therefore it sounds like your forward clutch is not engaged at the lowest line pressure, but engages when line pressure is a bit higher (either cold trans or revved engine).

OP, you say you rebuilt the trans and you have the Sonnax forward accumulator piston (which is good). Did you replace the forward and overrun pistons? The teflon seals on the input shaft?
As Dynamic396 suggests, checking line pressure at hot idle in is your best bet. If it is low (below 75 psi, assuming you have a 0.500 boost valve), I would fiddle with the boost valve and pressure regulator spring to raise that to 75psi. What boost valve is installed? If Transgo, did you remember the thick aluminum washer? If Sonnax, you need the 4l60E-LB1 and not the -LB2, assuming a pre-'05/'06 trans.

If the pressure is OK, perhaps one of the pro-builders (not me!) will have good advice.
Do you have the 4L60E Technician's Guide? Here is an online version of the guide:

http://www.grail-ss.com/GRAIL%20Webs...ETechGuide.pdf

Perhaps a study of the forward clutch hydraulics will give you more ideas of what to check. If line pressure is good, I would first try another VB.

mrvedit

It sounds like your forward clutch is starting to slip, probably due to a lot of miles, indicating a rebuild in your near future. The PCM is detecting the slip and is therefore commanding max line pressure which you feel as hard/firm shifts.

I have NO experience in swapping to a manual, but from what I have read here, a good manual trans commands a good price (often $2000+) and you still need all the clutch parts, clutch pedal, etc, plus a different OS for your PCM. On a budget you really need to have a donor car for all the parts.
A level 1 rebuild from sponsor Performabuilt is about $1200, and a level 2 from them or FLT is about $1600. Lots of horror stories about having a local cheapo-shop rebuild the trans.

flowride

Thanks for the info. Strange thing is that it's a relatively low mileage car for a 1998, with only 87k on the clock and I DON'T beat my car. The $1200 seems relatively decent, but the question then arises: what would an average shop charge for an install?

mrvedit

87K is on the low side. Also, I am not "sure" of my diagnosis, which also depends upon your description. First, you should put a scanner on it to see if there are any codes. Not all codes (immediately) turn on the MIL light. I have heard of labor prices around $600 for a remove/re-install of a trans.

flowride

Funny you should say that. My buddy just bought a code scanner for the same thing and has offered to run it on my car. Great minds...well, you and my work buddy. I can't speak much for myself, LOL!

HighMileageC4

MRV Edit,
I should have the Transgo .500 boost valve already. Confident the washer was installed correctly since when I did this 100K miles ago I did not have the warm engagement issue. I remember reading the TG boost valves may wear but I am not sure if thats internet rumor or fact.

Forward piston is a Billet piece (I believe Sonnax) and the overrun piston was reused since the drum is sleeved. New seals on both. Chuck at FLT helped me install the pistons since I live in Chicago area. Also a new stator shaft and new teflon seals were installed on turbine shaft and back of the pump. They were solid white seals. Chuck did these also.

If it helps the pros I can list out all of the mods, but in general the big things were upgraded:
Delco 5 pinion
Beast shell
Rollerized reaction carrier
all new bearings and bushings
New drum and wide band
New low roller sprag clutch Borg Warner
New Borg warner 29 element sprag (From FLT)
All Borg Warner clutches
Sleeved drum, billet forward. Special overrun (not sure if its billet)
TG High rev spring kit and drum bleed capsule
Sonnax billet 2nd servo and pin. Pin length set to low side of spec.
Sonnax billet 4th servo

Valve Body:
All NEW GM selenoids, PCS, and manifold switch
Transgo shift kit. No shims in accumulator. 1-2 is solid.
Sonnax 2-3 shift valve
Sonnax Reverse abuse valve kit
Band release checkball omitted and plate plugged
3-2 control valve spring removed and blocked inboard

Pump clearance was checked and about .001 -.0015 clearance. There was a small groove in the husing that I carefully smoothed with fine papaer.

Fwd clutch clearance was .070-.071

I did not put a new forward abuse valve in it.

Maybe the easy thing to try is a new forward abuse valve (but I do not see in Sonnax literature that it addresses this). and try a new pump boost valve.

The other ting I may try is bumping the very low throttle pressure tables up, but I want this as a last resort and want to address mechanically.

mrvedit

You obviously know these transmissions very well.
If you don't yet have a pressure gauge, you should get one. ($45 on ebay). They come with a long hose so that can hang the gauge from your outside mirror while you drive around. With the pressure info, I bet you can figure it out.
Or call Chuck at FLT and give him your pressure readings, he knows this trans 100x better than me.

HighMileageC4

[QUOTE=Dynamic396;17425531]Does it feel like it's going from a neutral condition and then engaging into forward when you give it throttle? Or does it feel like it's in a higher gear (say, 2nd...) and then dropping down into first when you give it throttle?

Does it do the same thing in manual low?


Dynamic,
It feels like a slight Neutral condition and then engages forward. You feel a small bump or engagement.

It does the same thing in manal low. Slightly better but still there. Would like your professional opinion.

I looked at the hydraulics and it looks like the forward abuse is in the path to the forward feed, although as I said earlier, nothing I can find in Sonnax literatue where the fwd abuse valve addresses this issue.

Also, confident I have the TG .500 boost, but maybe the spring has become weak? I am thinking just replacing the boost valve and spring because its easy and cheap enough for peace of mind.

What I will say about Transgo is I already had to replace a broken 2nd accumulator spring and the high rev clutch return springs were broken when I rebuilt the trans so I had to replace a few of those. Not good luck with their springs over the long haul.

MRVEdit,
Your help late last year was very valuable, all of your part number research helped me rollerize the reaction carrier and upgrade to 5 pinion planets. Only thing NOT done to this trans is Sonnax Shell (I already had the beast), billet shafts, and the smart drum. I am in no hurry to drop this thing, hopefully my problem is an easy fix, but next build will have the parts above other than billet shafts since I only plan on running a street tire.

HighMileageC4

Update.
I already had the sonnax reverse abuse valve and plug from the rebuild so I left that alone.

I put the same new valve and plug in the forward abuse location. The old valve looked ok but the new valve was a tighter fit. The old plug was also elongated at the pin and new plug had a smaller pin hole and is slightly oversized.

I also replaced the .500 transgo boost valve with the sonnax .490 valve with the o ring seals. The transgo valve had some scratches indicating wear. It was slighty looser but not rattling. The new sonnax valve was tighter and you needed pliers to get it out of the housing. I compred the transgo large spring to stock spring and to the new sonnax spring and it was shorter. I think this spring took a set. When removing the assembly I was able to push the housing into the bore and it would stick up making the c clip easy to remove. I am pretty sure the spring took a set here and wore out.

The results of this change are night and day. Problem has been eliminated. Going into gear is much more responsive. When tranny is hot I do not feel the bump and reverse to drive engages quicker.

I am pretty sure the fwd abuse and boost valve played a part here.

One other bonus is with the soonax boost valve the part throttle 1-2 shift is a little smoother. I have the transgo dual spring setup in the 1-2 accumulator and sonnax billet servos and the part throotle shift was bordering on the stiff side. Now its more progressive with throttle.

I did notice a small amount of black clutch residue in the pan. Fluid was still bright red. I should have done this sooner, but hopefully no significant damage was done.


Shift quality is excellent, These sonnax parts are very high quality.

mrvedit

Good to hear! And thanks for the detailed update and information.

A local trans builder told me that he experimented with wet testing the pump passages and noticed huge leaks past the stock boost valve; he didn't know if that was important, but it was clearly there, especially with high mileage valve bodies. In contrast, after installing the Sonnax boost valve with its two o-rings, there was no more leakage. Since then he installs the Sonnax boost valve in many rebuilds, even for "stock" rebuilds.
I suspect that Sonnax had a good reason for adding those two o-rings.

hollywood6964

I know this was many moons ago, but I'm having at least a similar problem. Did you have the same issue starting in 2nd gear when warmed up? I'm not having to bump the gas at all in R or 2, only D, 1 or 3.

This was rebuilt by a local shop about 50k ago by previous owner. He told me he lost first gear at a stop light when he towed it there. Sounds like this could be a similar issue w a worn valve body and sonnax parts may help me out here. Did you have to remove the valve body to install those two parts, or were you able to replace them without removing the VB? Also how long did that last you before the transmission gave it up, if it has? Any further info would be greatly appreciated, not a vet doing this, but I'm quickly learning and doing.

EDIT- boost valve inside the transmission on pump got it. Which one do you think helped the problem, or do you think combination of both?

bbond105

If you took a line pressure reading in gear at idle would go a long way in degerming your problem.

Yes, the boost valve can be replaced without removing the valve body. Depending on the year of the trans you may have to remove the pump. I think 2007 an up the pump has to come out.

Edward Stark

I had this once on my old Trailblazer. Did the following and not sure what fixed it :

-Replaced the Boost Valve
-Completely washed my VB.
-Reinstalled everything with a new FWD acum

Also, the OE Valve and sleeve was welded together from dirt like Putin to his throne.
Clean it.

And the problem was gone forever.

hollywood6964

I'm going to buy and do a line check this weekend. I'll get back w the results.