I have always had this problem with my SRT-6. When I'm going pedal to the metal the car takes ages to shift from 3rd to 4th, it just revs really slowly from 5,000rpm to 6,100rpm until it finally decides to shift.

When driving normally the car shifts fine.

Possible Causes

- Transmission problem e.g. t/q converter playing up or slipping.

I don't think its the cause because when driving normally it's fine & even driving flat out it shifts great in all other gears except from 3rd to 4th at around 100mph

- Intake manifolds not tight enough?

I've done them as tight as possible and the a/f range is very healthy if anything abit rich so I don't think theres a boost leak?

- My final assumption the supercharger pulley might be abit loose? thefore it's spinning but not engaging at a high speed going flat out?


I dont think anyone has had this problem but it's so frustrating as I cant go to the track until I fix this as we all know we need the whole 3rd gear plus a bit of 4th to cross the line going flat out.

 

I have the same issue on mine, but I only have on a NW intake

 

Your serpentine belt could be slipping once it hits full boost as well.

 

It's a possibility, however I've got my own belt wrap kit installed and the belt has virtually no slack in it.

I thought it had something to do with the NW Manifolds, I installed the standard intake mani's and the same problem occurs so nothing to do with those.

The worst part about my problem is I cant exactly take it to Chrysler or Mercedes and say "I've got a problem when I'm doing about 90-100mph's flat out the car takes awhile to shift from 3rd to 4th between 5,000rpms - 6,100rpms"

 

When it stops raining I'm going to take a in car video and show you guys exactly what it's doing.

I've never experienced belt slip nor do I know what it would feel like. Maybe some of you guys that have experienced it can confirm if that's what your car does when it's slipping.

John.

 

Hmm...Hope you get it straightened out. I always spray a little of the belt dressing on the belt/pulleys before I go racing to help prevent any slippage. Maybe you should try that just to eliminate the possibility there. Good luck.

 

I wonder if it's engine temp.

 

I run my car often with high temps (240º) and IAT's around 175º and it doesn't affect the shift. My car pulls strong from 5000 to redline in all gears. The shift is slow and sloppy IMO but always the same.

Les

 

I'll have to look for the thread on solenoids, but that's what it sounds like or possibly a spring in the valve body like this: Photo DIY- 722.6 Conductor Plate and Pressure Regulator Spring R/R - Benzworld.org - Mercedes-Benz Discussion Forum
???

I'm definately not an expert on transmissions, just throwing ideas out there. Good luck and definately post a video. I'll have my buddy, who owns a transmission shop in MA, have a look to see if he has any suggestions.

 

If the belt is slipping you should be able to find black 'dust' near the pulley(s) that it is slipping on.... I saw it at the SC idler pulley(next to SC pulley) before I added the NW pulley kit and took that pulley out....

 

with a c3 and a wrap kit it isnt likely theres any slip. at my max boost of 19 psi i never had any slip with the c3. i think alan has the right idea with the conductor plate

 

you need part of 4th for the quarter? My tune is set up to shift into 4th at the quarter...good luck with finding the problem....

 

Its hard to say what it is. Have you checked the transmission fluid level? Leaky manifold gaskets? Is it pulling lots of timing when you notice the longer shifts?

 

I keep thinking about the gaskets now as I've gone back to the OEM gaskets and I have re-used them a few times. Even if they were leaking very slightly I cant imagine it having this much of an effect. But then you never know!!!

Maybe I should try and spray some copper gasket sealant on them?



Thanks for that link Buggin I read through it but the difference with my car is other than when I'm going flat out at 100mph close to the top of 3rd. The transmission is flawless. Even hard acceleration from 0-70mph when it's changing from 1st - 2nd it does it great. I'm just lost here.

 

Kel, you can't reuse the gaskets....I would look for a boost leak, it does sound like that could be part of it...I am getting some gaskets to keep on hand...not really that expensive here, considering running lean isn't an option...

 

Thats the thing Doc my car is running rich if anything, from 0-100mph its in the mid 11 A/F range.

But I think the cheapest and quickest test will be changing the gaskets. If it still doesn't run right than it at least eliminates that out of the equation.

John.

 

Here's 2 short videos of my issue the second video probably shows the problem better. I'll do another one soon. The delay gets worse the faster I'm going

Delayed gear change - YouTube

http://www.youtube.com/watch?v=bkZTq...ge 2 - YouTube

 

I bought some Permatex gasket sealant put everything back together hoping for the best. Unfourtuantly it's no different I wonder if it has something to do with the tune.

John.

 

Could be the clutches going away in the 4th clutch pack. The clutch friction material is a wear surface, and with useage and increased hp, sometimes they do not have sufficient holding power.

 

Possibly. This is assuming that 3-4 upshifts manually done are fine at that speed. The tune would affect shift levels to an extent. If you have an Aeroforce scan gauge, you can monitor some of the OBD-II parameters and log them to compare. I think they log for about 60 seconds internally. External logging is possible with another cable. See:

Google

Dual-model on an SRT-4

Aeroforce SRT4 gauge demo - Car Videos on StreetFire