# Safe-T-Track fluid viscosity



## wishihaditback (Jun 9, 2011)

I wouldn't have thought this information would have been so hard to come by that i'd have to post this Q. What is the correct differential gear oil viscosity for the Safe-T-Track rear end in my '68? I do know about, and have, the GM additive, but can't seem to find the oil info. No, i don't have the owners manual. Secondly, the previous owner who changed out the fluids said he couldn't remember what he used, but that it was blue, and when i mentioned Royal Purple, he thought that might have been it. If that IS the case, RP advertises it is compatible for limited slip rear ends, but does anyone know if it is more than adequate for the older LS rear ends? Perhaps i should just start from scratch if i can find the proper oil viscosity. All input would be appreciated.


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## GTO JUDGE (May 14, 2005)

wishihaditback said:


> I wouldn't have thought this information would have been so hard to come by that i'd have to post this Q. What is the correct differential gear oil viscosity for the Safe-T-Track rear end in my '68? I do know about, and have, the GM additive, but can't seem to find the oil info. No, i don't have the owners manual. Secondly, the previous owner who changed out the fluids said he couldn't remember what he used, but that it was blue, and when i mentioned Royal Purple, he thought that might have been it. If that IS the case, RP advertises it is compatible for limited slip rear ends, but does anyone know if it is more than adequate for the older LS rear ends? Perhaps i should just start from scratch if i can find the proper oil viscosity. All input would be appreciated.


In my 3.55 Posi I have 75W or 80w in there. I'd have to dig into my records to verify but 75W is what I believe. Either or you'd be good. Brand? Valvoline. I have FM in there too.


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## Pinion head (Jan 3, 2015)

Nearly 2 quarts of 80-90 w a bottle of GM posi additive. Install one quart of 80-90, then then the posi additive, then less than the next quart of 80-90 till the grease comes out the fill hole. I usually install before installing a fresh built rear, but in customers car, on the lift, depending on exhaust system, can either use plastic bottles or in a tight fit, use my old gutted grease gun with extended hose.


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## wishihaditback (Jun 9, 2011)

Thank you muchly!


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## GTO JUDGE (May 14, 2005)

Checking my records this is what was installed in my Pontiac rear. 


Valvoline 80w90 1.75 quarts+4oz Limited Slip additive


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## wishihaditback (Jun 9, 2011)

Thanks for your help. I think that's what i'll use.


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## 1968gto421 (Mar 28, 2014)

Sorry that you couldn't find the post I did back in March, 2015, on this topic. Members gave some great info as they did here. I'll post the link if you want to check it out: http://www.gtoforum.com/f50/what-best-lube-sure-grip-rear-83730/
Hope this is helpful.


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## wishihaditback (Jun 9, 2011)

Thanks for the link. I tried a "search" on this subject before i posted and didn't see yours from March. The "search" engine must be very word specific and/or there tends to be a ton of results that don't always seem to deal with the desired subject. So far the results have been narrowed down to a 80w90 or 75w90 and using the additive. Thanks to all once more!


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