goredcar

Hey guys... would appreciate some advice. I recently went FI and added the Stillen V3. Since then I am noticing a bit of an issue with a 4-6 shift in that it will not go into 6. This is on hard acceleration in third, then hitting 4th hard... by then I am going too fast and I slide from 4-6. When I was NA this was never an issue. Now it is just not going into 6th. I have experimented with blipping the throttle before the shift and it goes in fine, but I never had to do this before. Clutch is stock. Transmission fluid just changed. I went with a cocktail suggested by Ryan of RJM Performance (the clutch pedal guy). On a forum quite a while back he mentioned that he'd tried multiple fluids and combinations of fluids and gave his thoughts on how they ranked. The one he liked best is 1 part Amsoil Synchromesh manual transmission oil to 2 parts Redline MT85.

Any suggestions as to what is going on? Are the synchros not responding well to the HP increase? WHP is up by 159 from 284 to 443.

JSolo

iTrader: (14)

Blipping the throttle on an upshift?

I figure there's at least a 2Krpm difference between a 4th and 6th gear at the same speed. If you're not letting it drop by at least that much, getting into 6th will be difficult. Also, from what I recall, 6th has a single syncro while lower gears have additional which helps smooth engagement. Might also try double clutching the upshift.

Take a look at the attached pdf, it's based on calculated speed vs engine rpm based on stock gears/tire size. It doesn't take any other factors into account.

goredcar

Thanks for the chart... it's a good reference. I really don't think rev matching on upshifting is necessary, only on downshifting. When I do shift from 4-6 I basically want to stay at the speed I am at not accelerate further so I back off the gas and revs drop quickly. This never used to be an issue for me bore the SC install, so I am wondering if the additional forces are causing some linkage misalignment. I read on a 370 forum that some guys had issues with the shift plate getting a little loose and misaligned and had the same difficulty as I am having going into 5th and 6th. Apparently there bolts that hold the plate in place and they can get loose over time. Maybe the additional HP amplified a problem that I already had?

RadioFlyer

iTrader: (1)

Do you know the condition of the clutch? Has it ever been changed? Possible the throw out bearing was put back in wrong? IF the only thing you changed was the fluid since the problem started happening, go back to the original fluid and see if the problem persists. If so, check something mechanical, if not, then your tranny doesn't like the cocktail.

goredcar

Original clutch... still in good shape. I'm also thinking that the tranny may not like the blended fluids. That sounds like a good place to start. It just seems odd to me that this is only on a hard pull. With normal driving it goes 4-6 no problem.

RadioFlyer

iTrader: (1)

I have that problem with my other car. After running 4th to Redline, it feels like I'm getting 5th, but then it grinds. I've checked everything, and I'm chalking that up to deflection in the tranny case very slightly misaligning the innards. But that' a different car and a different story... These Nissan transmissions should be pretty stout. Is there any possibility you might be low on fluid, so the 6th gear synchro isn't getting bathed and therefore isn't spinning up?

goredcar

Thanks Radioflyer... I have my car in the shop on Friday to get an oil change and I will have them look at tyranny fluid level. Appreciate your suggestions!

goredcar

I was doing some testing and my RPMs are a bit higher than what is shown in this table. For example, at 70mph I'm at 2800 in 6th, not 2600 as the table indicates. Is there some variation in rear end ratios in the G coupes?

I had my car in the shop and they checked the shift plate... everything was tight and looked good. The mechanic does not think the fluid has anything to do with it. Went for a drive and was able to demonstrate the problem to him.

JSolo

iTrader: (14)

The numbers in that spreadsheet were based strictly on the criteria quoted. IIRC, the tire size was based on the front wheel (225/50/18) from tirerack's tire spec for the RE050A.

The difference can result from different tire size (rolling circumference), error in tach readout, and it doesn't account for friction/resistance. At higher speeds/gears the error amount increases too.

Does the car shift smoothly if you don't skip gears in the upper revs?

goredcar

Was out with a few friends yesterday and did some experimenting. Sequentially shifting does not make any difference (not skipping gears on upshift). The only variable that causes a problem is hard acceleration. Not sure why front tire is relevant for a RWD car RPM calculation. My stock sizes were 225-45-19 Fr and 245-40-19 Rear. I am up one size on the rear to 255-35-19... which is very slightly smaller in diameter so that may explain some variance.

JSolo

iTrader: (14)

^^You're probably right, I could of taken the measurements off the rear. I'm not sure why I used the front.

Smaller diameter tires will have to spin more to cover the same distance, so your rpm will increase slightly.

Here's the link if you want to recalculate your own:

http://www.f-body.org/gears/

goredcar

Thanks for the link

On the shifting issue I have an appointment on Thursday to get the tranny flushed and go back to Nissan gear lube. Will let you know if that helps any.

goredcar

Ok... so here is the update. Ryan of RJM Performance recommended a tranny fluid cocktail that was total **** in my car. I went back to Nissan fluid and my shifting problems are gone. Lesson learned!

JSolo

iTrader: (14)

I was running redline MT85 for about a year and half (8K miles). Last winter had a really had time shifting in the cold when cold (trans). Replaced with nissan fluid, shifting improved. We'll see how it does this winter. First winter with mt85 was great, no issues at all when cold (esp 1-2).