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Depends on how you use it.

4500 rpm launches and WOT shifts w/ 500ft/lbs of torque eventually did in my input shaft. Everything else seems to be ok, but I haven't taken the tranny apart yet.

The biggest weak link seems to be the input shaft. Another 1/8" or 1/4" bigger and made out of a stronger material + heat treat + cryo should do wonders.
 

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All transmission/transaxles are rated in torque, and New Venture Gear rates the maximum input torque for the NV T850 used in the SRT-4 to 250 ft-lbs. :)

It will take much more than that, but you will start degrading long-term service life and durability the harder you push it. Equally important to how much power you're asking it to handle is how you drive it. Treat it nice and it might last for a while at 500 hp. Beat the heck out of it and it might fail pretty quickly at 350 hp.
 

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Well, I will disagree with the 250 lb/ft rating listed above. Two years ago (when I bought my '04), I made a phone call to my friend at NVG who IS the Engineer that designed the gas version of the T850. I asked him how much it could handle and he answer was simply..."You won't be able to break it!". Now, some people out there have had failures which I would blame on abuse. And yes, they (NVG) have even made some running changes on a couple of things. Let's also understand that DCX has to provide warranty on these and you will get a much more conservative rating from them.
 

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They apparently don't update their web site too much, but it's listed right here:
http://www.newventuregear.com/transaxles.html

I was also browsing some of their company documents one night long ago and found a similar reference. Like anything it's more than likely what they've rated it to under testing for durability. And on a stock car it should run 150k miles or more without problems. But who knows? Maybe it would pass the same testing and certification at much higher power levels but DCX didn't see the need. Either way, on cars pushing a great deal more torque than stock there's sure to be more "issues" as the mileage racks up as we've already seen in the real world.

On a side note Tim, I can't remember if we ever met at the SoCal SDAC meets before you moved. I'm not sure many people on the forums know your history with the ancestors to the SRT-4. :) If you talk to your contact at NVG again I'd love to know how the strength of the T850 compares to the older A568 in their testing. I don't think I've ever ran across any figures to show what those were rated to but they've held up extremely well under hard use.
 

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shelby guru said:
Well, I will disagree with the 250 lb/ft rating listed above. Two years ago (when I bought my '04), I made a phone call to my friend at NVG who IS the Engineer that designed the gas version of the T850. I asked him how much it could handle and he answer was simply..."You won't be able to break it!". Now, some people out there have had failures which I would blame on abuse. And yes, they (NVG) have even made some running changes on a couple of things. Let's also understand that DCX has to provide warranty on these and you will get a much more conservative rating from them.
Well, the transmission seems to be fine... it's that stupid smallish input shaft.
 

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OK, I just got off of the phone with the Engineer at NVG. The "official" number that should be on their website is 265 lb/ft of torque. When I asked about the input shaft "stress crack / failure" issue they have traced that back to a Stage 4 non-sprung hub clutch that was not self centering on the shaft. This causes an imbalance issue that when combined with the on/off nature of the clutch material creates a bending moment being applied to the torsional load of the shaft. The real interesting "piece of information" was that the input shaft has been tested to steady state torque loads of 1,000 lb/ft before failure occurs!
For the older school of previous transaxles out there, here are some other values:

The A-568 was rated to 230 lb/ft. and the 555 with the 18 spline shaft was 215 lb/ft.
 

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Thanks. :thumbsup:

I know quite a few people that have had issues with sprung hub disks. Maybe they haven't seen a large enough sample of failed units with all the different combination of factors to say for certain. Their explanation may very well be valid for some cases. I was originally wondering and posted before about if there might be an issue with the bearing assembly or something else wearing improperly that was allowing the input shaft to flex/break. That's probably one explanation, but I bet there are others that are simply failing due to abuse and or being pushed way outside of the design limits. The shaft may be pretty strong but if there are other weaker components or changes made such as aftermarket parts (i.e. modular clutch assemblies) they those may also compromise it.
 

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mchat said:
Well, the transmission seems to be fine... it's that stupid smallish input shaft.
Well i dont belive they designed it to run 9's from the factory. It has run many many 11's and a 10 so far so how bad could a stock tranny be.
 

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shelby guru said:
The A-568 was rated to 230 lb/ft. and the 555 with the 18 spline shaft was 215 lb/ft.

Perhaps I should tone down Sledgehammer a little bit, eh Tim? :thumbsup:

The 568 Tim spoke of has endured many hundreds of launches in my GTC, (It's a Lebaron for those of you who do not know). Upwards of 6800 and a few that have tickled my 7200 rev limiter. Same shaft as the SRT4, but I use a sprung hub on my 4 puck clutch. Just a 568 with a Quaife.........

The 555 transaxle has taken a good friend's Omni to a best pass of [email protected]
 

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So Mr. Menegon, do you plan on picking up an SRT-4? Seems quite a few names from the old SD/TD mailing lists are popping up over here. :lol:

I know you somewhat retired, but if you ever decide to try some work on the SRT-4/Neon heads I've got a couple of them sitting around. :thumbsup: As for the 568's, they've held up very well in some of the heavier cars, especially the R/T's. I'd almost bet they'll do better over the long haul than the SRT-4's trans.
 

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ok, if the fail rate is at 265 tq, then how can the tranny with stand S3, or other cars that are over the 450tq rating? dont understand that part....please explain....
 

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That's just what they're tested to for extended durability of a 100k, 150k, or however many miles DCX/NVG specified with a certain percentage of failure rate. No one's saying they can't stand up to a ton of power, just take 100 stock cars and 100 heavily modified cars and one group is going to have more failures, worn components, etc. If you go over 265 ft-lbs there may be more potentials warranty issues than is acceptable to the bean counters (all warranty work comes back as an added expense). That or maybe its just the most they tested it to because DCX the car company never planned to pump more than that through the transaxle.

Also Stage 3 and the other "Stage" kits are offered by Mopar/MP, which you can think of as a completely separate division in DCX than the group that makes the cars. I'm sure Mopar and the SRT team did a ton of testing with their kits, but they are essentially like an aftermarket parts company owned by DCX. That's also why they say for "off road use only" and you'll void your warranty if a related powertrain component fails.
 

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I have one! I bought a 2005 ACR back on October 18,2005. She just turned over 31,000 miles! I use the car for my work as a Courier. I had to have a fun ride for working. I do have some issues with the trans in the ACR, but I'm not beating on it. Hell, I've yet to pull a quick shift in it! The car is more of a "tourer" for me.

I am semi-retired from doing head work, but I still do a few here and there. Yes, I do have my hands on the SRT4 head, but that project is slated for another day. I'm currently working on a new 8V head for the destroked 2.2 I'm going to run in Sledgehammer. The old 8V head is getting the ports raised 1/2" and I'm bringing the chamber out much closer to the deck. A good friend of mine did one a few years ago like that and the thing flows close to the 16V head. Hopefully I can get close to his results.

I did a few of the 16V heads for local guys. Mike Marra's brother Joe has one on his car and he went [email protected] something running 13psi on his first pass at Cecil. Nice to be a small part of the package on such a cool, fast ride!





blackbird_R/T said:
So Mr. Menegon, do you plan on picking up an SRT-4? Seems quite a few names from the old SD/TD mailing lists are popping up over here. :lol:

I know you somewhat retired, but if you ever decide to try some work on the SRT-4/Neon heads I've got a couple of them sitting around. :thumbsup: As for the 568's, they've held up very well in some of the heavier cars, especially the R/T's. I'd almost bet they'll do better over the long haul than the SRT-4's trans.
 

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Sounds like an interesting project. I remember a lot of your posts about head work from the FMML years and you were also on the R&D list, correct? I look forward to seeing what you can get out of your car. :thumbsup:

I know the 8V guys still hound you for head work, but if you do decide to do some more work with the Neon heads I'd definitely be interested (I could also provide an extra head if you wanted to cut one up). If that's something that interests you or you have a waiting list drop me a PM. My engine is coming apart for a build up right now and it would be nice to help the top end breathing that feeds a little GT35R. :)
 

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Srt-4 Tranny is weak

Hopeful they make a whole new up grade for the SRT-4 the tranny then the driveshaft and axels and all that stuff :flame:. I've got 400hp and 400ft/lb of torque. I only have 5000 mile on me car I got it with 88 miles from the dealer. I pimped out the engine at four 4000 miles. I take it to the track with *NOTE THIS* STREET TIRES !!!!! I get 2 good runs out of the thing. 3rd run :rollout: Bang blow Tranny. :tongue: :Wtf3:
 
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