Fluid recommendations...., Tranny and rear Options

[396 Hawk]

Even though I don't track my Hawk (for now), I figured I would ask some of you race guys what you use in the tranny (M6) and rear (4.10 10-bolt) of your cars.

I'm going to change all of my fluids in the next week or so and have used Redline in the past with pretty good results but have been considering Royal Purple.

Any suggestions?

[bobbylee]

I use Amsoil universal ATF in the trans. There are several Amsoil products for the rear - product code AGL 80W-90 standard gear lube, SVG 75W90 Severe Gear lube, or SVO 75W140 Severe Gear lube. You can run the Amsoil lubes without any additive; if you get any chattering with a limited slip add a friction modifier. I have used the AGL product for several years, and am changing to the SVO later this year. Another excellent gear lube is made by Lubrication Engineers. Their products are Almasol (mineral), Monolec (additive enhanced), and Synolec (synthetic). I formerly used LE's Almasol in all my vehicles. The gears in my van used for heavy towing looked like new even after 100k. For over the counter stuff at any auto supply, Pennzoil 4096 gear lube is hard to beat also.

[Judd]

If you can not get Amsoil {good oil but the craziest supply system} try GM's Syncromesh for the tranny and a good synthetic 75-140 for the rear. In the tranny I've tried the stock fill {Dextron ATF} and Mobil 1 synthetic ATF. I didn't like the M1 at all, made the shifting very notchy. I replaced it after about 5K miles with the Syncromesh. I've had the Syncromesh in for around 35K miles now. BTW, the Syncromesh was recommended by a Ford guy who read about it in a Ford magazine for use in T5s. If Ford folks will recommend a GM product, it must be good.

I normally wouldn't run a 140 weight rear fluid in anything other than my 4 wheeler but I think that the 7.5 rear axle needs all the help it can get. I figure that the extra viscosity might help cushion the gears a bit. Haven't broke a 10 bolt yet and I have about 250 1/4 mile passes and about 200 AutoX passes on three different rear axles in 45K miles. Maybe it works maybe it doesn't but it makes me feel better. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/wink.gif) (IMG:http://www.frrax.com/rrforum/style_emoticons/default/biggrin.gif) If you have a Torsen {which you should have unless you optioned the Auburn}, you don't even have to worry about a friction modifier.

[KeithO]

In my old LS1 and my current LT1, I generally use Red Line D4 in the manual trannies and Red Line 75w90NS in the rear end to help the weak posi's work. It just so happens that the LT1 M6 currently has Amsoil Synthetic ATF in it, but is is because I had a bunch of it laying around... I've had no problems with the Amsoil, but I will be getting Red Line for the next tranny change (which will be soon).

I'd be interested in other road racer's opinions in the gear oil - should I be going thicker?

[pknowles]

I use Redline 75-90 in the rear and Valvoline standerd ATF for the tranny. I find that my tranny gets notchy after about 10k miles or 1 year and I need to change the fluid. In fact I just changed it this weekend and it shifts smooth again.

[robz71lm7]

Redline 75w90 regular or shockproof. If I were running road courses I'd switch it to 80w140. I run Pennzoil Dexron III and change it every year or two in my T56 (need to do it again). My tranny didn't like the synthetic dexron III's very much.

[trackbird]

I've got Mobile 1 in my trans and it works just fine for me. I have about 30k on the fluid and need to change it (maybe this weekend) and change the gear lube as well (still stock). I may try Amsoil (Jegs has it) or stick with M1 or I might try the redline, I'm still not sure.

[AllZWay]

In my Camaro I use Mobil 1 throughout and have had great luck.

In my dirt track car I run Royal Purple in the tranny and rear end.

[Teutonic Speedra...]

I've been using Redline D4 ATF in the tranny and Mobil 1 75/90 in the rear with no problems. (30ish track days)

[sgarnett]

The gear oil choice for the rear depends on the diff your are using. I used Redline Heavy Shockproof with the OEM T2, and I use Redline 75W90NS (nonlimited slip additive) with the T2R.

I am currently using Redline High-Temp ATF (basically a thicker version of D4) in the tranny to help quiet the trashed input shaft bearing (damaged by a defective pressure plate almost two years ago, but it hasn't blown up yet) and reduce the false knock-retard when the bearing is rattling. It shifts marginally OK when warmed up, but really sucks when cold. Reverse can be a real struggle on a cold day.

D4 was better.

By far the best-shifting fluid I used was conventional, non-synthetic Castrol D3. Mitch recommended it and reported that it was holding up fine on his backyard track in the Texas heat. My experience matched his - it shifted great and looked brand-new coming out.

I haven't tried the GM Synchromesh, though.

Personally, I think that while the gears may like a heavier oil film, the synchros DON'T - the thinner the better. Obviously it has to be a compromise, but the gears apparently have plenty of design margin (unless you are making a LOT of power) while the synchros are marginal from day 1. How often do you hear about somebody wearing out the gears in a T56? The T56 is supposedly a fairly efficient transmission, meaning it doesn't burn up much horsepower as heat, which means the gear train is well-designed for low friction.

[bigshoe]

I have d4 in my tranny and one of the redline fluids in my rear (synthetic 75/90 rings a bell?).

Now, i do remember reading something on one of the ls1 forums that synthetic tranny fluid is a bad idea (for the t56, or at least the ls1 t56 if there is a difference) had something to do with having paper liners for the syncros or some other part, and the synthetics would eat it apart after time. I don't know of any truth to that, but i figured its worth mentioning here.

personally my gearbox is probably fine, but now that i'm paranoid, it does gring going into 5th when cold, and its been tough to get into 1st from a stop unless i double clutch sometimes. I have nearly 80kmiles, gone through 2 clutches, and my driving style is probably considered spirited. don't konw about the owner that put the first 19kmiles on her though....

anyone else heard about synthetics being a no-no for the t56? I think i remember something like the viper t56 is immune to this problem, and possibly the c5 t56, since they didnt use the cheaper paper lining?

[sgarnett]

There's been endless discussion at sites like ls1.com of which T56 models can safely be used with synthetic and which can't. I don't think it's ever been resolved.

To me, it comes down to this:

The conventional D3 simply shifted the best in my tranny. I'm happily using synthetic in my engine and diff, but if it wasn't for the bearing problem (which was caused by a bad pressure in about an hour of driving, NOT an oil-related failure) I would switch back to the Castrol D3 in the tranny and never look back. Whenever I get it fixed, I WILL switch back.

[Spooner]

My theory has always been that most people who say that switching to synthetic fluid killed their trans had a trans that was already well on the way from them beating on it. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

But I plan to stick with regular D3 in my car, since it's working fine and the trans shifts well... Glad to hear that the Castrol works well, since it's readily available.

-John

[bobbylee]

I dumped the factory fill at about 1500 miles on my 97 and have used Amsoil synthetic ATF since. No problems.

[Rob 94Hawk 319]

Maaan.. Just use some stuff from Phantom Lubrication for that Phantom Hawk!!!

I've used redline with great results in mine.

[Soma07]

FWIW I've run the following in my T56:

1. Whatever was in the car when I bought it
2. Mobil 1 ATF
3. Honda ATF
4. Castrol D3 ATF

To be honest I couldn't tell a difference between any of them. My tranny has over 200k on it now so its not like its brand new either (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

[Honda93]

A resurrected post and it's not even Easter!

I've been using Amsoil in the motor, trans, and diff since I got the car in late 2014. Love it!

Just changed the trans and diff fluid today, and my dumb*** self forgot to drain the Amsoil hand pump I was using (the hose was all but empty, but I forgot to expel the remaining ATF in the pump cylinder itself), so I actually put 2-4oz. of their Signature Series Dexron III ATF in the diff mixed in with their 75W90 Severe Gear EP stuff I use.

I should be OK. Yes?