ndnJedi

I'm planning to get my E4OD transmission rebuilt in my 2WD 91 S-Cab by about November. It started slipping in 2nd gear the other day and fluid level is in the crosshatched area when hot and idling on level ground. It will be parked basically until it gets rebuilt, has 455,xxx kms(283,xxx miles)

Anyways, my question is: how long after the rebuild until I can switch to synthetic fluid?

It'll be a full rebuild where everything internally is replaced including torque converter, no sense in only replacing some parts with the possibility of having to do it again in a few years. Quote so far from one shop is $2500 all parts/labour/taxes/fluids included and me dropping the truck off for them to do their thing. Asked a few other shops for quotes as well, no response from the others yet. But that is what I was expecting, i'm sure it may be cheaper in US, but this is just down the street from me here in Vancouver, Canada

qdeezie

I don't know what fluid you're using at the moment, but if you're not using a high mileage ATF, you might want to try using a high mileage ATF to see if your shifting improves. My truck shifted horribly off of lower quality fluids and it shifted like I put an entirely new trans in it once I went to Valvoline Maxlife ATF. I hear that Castrol High Mileage ATF is another one the E4ODs like alot.

Regarding the synthetic question, I've never known a trans to require a break in period, however, I'd imagine changing over to synthetic anytime after 10,000 miles should be ok.

ndnJedi

Yeah, I don't know what fluid it has either, the fluid is what came with the truck and I haven't changed it. I might try that before going the full rebuild.

But I have gotten some more replies on quotes, one place is $1500-1600 just for rebuild and new torque converter. So it might just end up getting rebuilt and maybe sooner than November. So the other place that quoted $2500 must've added like $1,000 for re/re of the trans. I can do the re/re myself no problem, save $1k!

bluecar5556

Switching to a synthetic after it's been running conventional for so long might be a bad idea, in some cases the seals might start to leak due to synthetic being less viscous (thinner) as far as ENGINES are concerned.

I've not witnessed this personally but was told so by many instructors at UTI, so consider the source, i'm just relaying information.

Follow manufacturers recommendations: Mercon V conventional, does not mention anything about synthetic. Besides, there is nothing different between conventional and synthetic oils as far as the base oil is concerned. The ONLY difference is added synthetic additives that last longer. The base oil does not break down, only the additives, that's why oil is recyclable. The same amount of trash (clutch material in trannys and byproducts of combustion in engines) are still going to accumulate regardless, so why not change the fluid more often like the manufacturer intended?

NOTE: Changing the ATF fluid on a transmission that has over 100,000 miles without the ATF ever being changed will more than likely only make things worse. ATF fluid is high in detergents meaning it is a very good cleaner. This will dislodge trash accumulated throughout the transmission and deposited it in the valve body (a bunch of worm holes of very small diameter) and stop it up.

94Bronc

If you're worried about crap coming loose and gumming up other things do a flush. Bad fluid obviously would be bad to have...I've done trans flushes and services enough on high mileage cars and trucks and never seen a trans failure due to changing fluid. The only time I've even seen a "mechanic" not want to change it was firestone. I think the view on changing fluid is one of those things that was good advice way back in the day but doesn't hold true anymore.

bluecar5556

You mean when transmission flush machines did not exist not too long ago? Still, people do a drain and fill to save money rather than spending $70-90 to get it flushed. Thanks for clearing that up, do not change the ATF using the drain and refill method with a ton of miles between changes, go and have it flushed if you want to roll the dice!

ndnJedi

Thanks for the very informative reply. I have gotten more reasonable quotes from some more trans shops. Still up in the air about changing the fluid. Probably won't change it as i have been told the same info before.

bluecar5556

I personally would not change the fluid. If there is any damage to the clutch packs, the damage is done, no fluid will repair that. If the fluid additives are broken down where it is thicker, that would usually lower the line pressure of all clutch packs, not just 2nd and would make all gears slip. Does that make sense?

94Bronc

My point was more that transmissions are built differently today then they were back then. There's a filter in there that's designed to catch all the crud. Leaving old fluid in there would cause my problems in my opinion. A flush would be better of course but I haven't seen issues with a filter/fluid change.

94Bronc

Old fluid loses it's lubricating properties.