Friend has rebuild 833 for his 70 RR.
He's racing the car and was wondering what's the best oil to use and why.
Thanks for info.

A couple of racers here on Moparts recommended Pennzoil Synchromesh oil for the hemi 4 speed in my dad's 6 pack road runner. It's just a street car, but seems to work great.

He had some light oil in it from grey can. Doesn't know name.

If you are using the regular brass sync rings all you need is good quality auto trans fluid. That's all we have ever used in the 833 in a drag application, dating back to the late 60's. Works great when it gets cold out too. We used it in the old overdrive units based off the same design as the 833 for field complaints of high shift effort when very cold. These older units were called New Process 440's. Some people will tell you the trans will fail with this fluid - we ran them behind pro-stockers before the Lenox showed up and we used them in MP, Comp, SS and Stock Eliminator cars this way too. Never saw an issue in any application. Not to confuse - the units used In drag racing were the 833, not the 440.

Chrysler used auto trans fluid in the overdrive 4 speeds. BUT they had issues with premature wear on the thrust bearings and synchro rings.
We received a service bulletin when I worked at the dealership in the 80's that said replace the auto trans fluid with regular 30 or 40 weight engine oil.
IF you guys will remember in the 60's and 70's transmissions came with something like 90 weight gear oil in them.
I ran 30 weight oil in my Super stock Hemi 833 Hemi trans with a little bit of STP for the slick stuff it had in it.
Never had an issue.

Agreed,
My dads 73, 340,4spd duster he bought brand new had ATF in it, still has today, been thrashed at the track it's whole life and has 100k on the odo. Best shifting trans I have ever shifted, feels and works like brand new.

I used ATF way back then.. if I didnt use that
it didnt like to shift.. was a high reving engine

The SAE grading for motor oil and gear oil is not the same.

70w80 gear oil is about the same viscosity as 15w50 motor oil.

Not all production early Mopar muscle cars with NP833 came with 90 wt. gear oil in them, a lot of the cars sold new in the colder climates had ATF in them from the factories starting in 1965 or 1966
I had a 1965 Dodge Coronet 500 361 that came from new England that had ATF in it from day one according to the original owner I lived in the Mojave Desert at that time and switched the ATF fluid out to 90 Wt. gear oil, not a good idea in the winter
I put ATF back in it and used ATF in all my NP833 after that, race only or street and strip

It's 2017. No need to use ATF. A good synthetic gear oil will allow easy shifting in all climes. The bearings will thank you.

If it was me I'd use Redline MTL. https://www.summitracing.com/parts/red-5...ASABEgIL5fD_BwE

I use a 50/50 mix of synthetic gear oil and ATF+4. Has always worked fine for me.

I used that same lube in my Richmond and I also tried it in my current street HEMI box with syncronizers and it shifts like butter. I have seen too many cluster pins and gears worn out from ATF. IMHO the ATF doesn't have enough lube to keep the gears happy
Gus

Unit loading is much lower on manual transmission gear sets than planetary gear sets used in an automatic trans. I dont recall ever seeing worn out planetary pinions -not even at over 200K in units using Dexron or ATF III.

As for wear - be careful what unit you are talking about. The 833 is straight through power flow in 4th gear, the OD/440 has an overdrive so that load is unique to this unit.

As for going from ATF to engine oil - my recollection was due to it causing neutral gear rattle. Engine oil quieted the rattle. Sync wear was caused by the original gear oil causing brass ring to cone hydroplaning when cold - ATF prevented the hydroplaning. As for thrust washer wear - don't recall seeing that either - the thrust loads in a manual are not any greater per square inch than an auto thrust bearing. In fact the thrust bearing between the front carrier and annulus is probably greater than any manual trans would see. Lives quite well until you get around 800+ lbs. of torque. Way past what Ma Mopar intended.

Redline MTL here also.

Redline MTL is the way to go. It is what I put in our V code Cuda. I also run it in my Jericos.

Dexron ATF here also. Works fine for me..

Pennziol Synchromesh here. good stuff

My 65 has had 80w gear grease since I got it in 69.Was OE at the time and stillhas gear grease in it.It was a daily driver for years with gear grease and never a problem shifting.Rocky