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Oil Pressure and Angles


MJIbex
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I am again after some help, ideas, advice!

The truck is suffering from two different oil pick up problems on extreme angles.

1. When pointing downhill engine oil pressure drops to well under 10 PSI. GMC 6.2 Diesel.

2. When pointing uphill gearbox loses oil pressure = no drive. GM 4L80E.

Anyone else run either of these and had the problems; if so how have you sorted it.

I'm thinking of either different/modifying sumps and pick ups for both. Though the idea of dry sumping has been suggested. Has anyone done this and/or is it overkill?

Cheers

Mark.

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that's a rare box you've got there mark- what T-case are you using?

what sort of angles are talking about here? Do you 100% haev the right dipstick and are you therefore certani that the box is full of oil? these are fitted as stock to some pretty mean off roading trucks in the US who use them for rock crawling and i haven't seen any reported issues on pirate or similar.

you can buy baffled 4l80 sumps as well as extra deep pans with an extended pickup.

are you on an electronic or manual valve body? if the former then there could be the potential that the line pressure is dropping out and the box is defaulting to neutral- on a manual vale body obviously this isn't a problem!

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Cheers for the reply.

that's a rare box you've got there mark- what T-case are you using?

LT230 on 1 of "Mark's Adaptors"

what sort of angles are talking about here? Do you 100% haev the right dipstick and are you therefore certani that the box is full of oil? these are fitted as stock to some pretty mean off roading trucks in the US who use them for rock crawling and i haven't seen any reported issues on pirate or similar.

the far side of 45 deg on gearbox drop off and 55 deg on the engine (guessing, not the kind of stuff I would normally drive up or down without winch.) I chucked an extra litre of ATF over max in at the last challenge and then did not find anything steep enough after that that would give a problem.

you can buy baffled 4l80 sumps as well as extra deep pans with an extended pickup.

I was thinking of B&M

are you on an electronic or manual valve body? if the former then there could be the potential that the line pressure is dropping out and the box is defaulting to neutral- on a manual vale body obviously this isn't a problem!

On Electronic, the computer read out still shows first selected, I think.

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i'm not the only person with a marks adaptor kit in the Uk then :D - were you happy with the finish of the machining on the kit?

B&M are expensive- i have had a lot of stuff from PATC transmission centre and a lot of advice from them too- they do some nice pans and pickups that might work for you. If you were really desperate then you could fit a pre-oiler- which basically adds pressured oil back into the system automatically whenever the return line pressure drops- it's a oneshot solution but it would work for 30 secs or so i think.

If you end up running the box overfilled then you might do well to get a locking dipstick if you don't already have one- would at least stop hot oil squirting out of the dipstick.

You might like to look under the auto section at www.ls1tech.com for specific 4L80 problems- they have some fairly knowledgeable guys on there and there are a huge number of auto box builders on there too

i don't know a huge amount about electronically controlled gearboxes, but i am pretty sure from the tuning threads i have read on LS1tech that actual gear maintenance is controlled by line pressure in the box- the controller might think it is in first but still be dropping out actually in the bog. A much better person to ask would be Eliot Mansfield over at www.mez.co.uk as he has a habit of rebuilding 4l60e (controlled in a similar manner- certainly one controller can manage both boxes with a little reprogramming).

have you had any clearance issues down the side of the box with the front prop? With portal axles i'm really struggling for clearance but id' be interested in whether or not you have problems with stock LR axles- I presume that you are on a solid bar propshaft.

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Since I have to admit to being a bit of a cheque book off roader; due to not having the time or tools to do the bigger jobs, I have not really looked in depth at the adaptor!

Cheers for the links I shall have a peer at some of those in more detail.

I have major clearance issues with exhaust and props underneath; its a bit of a miracle it all fits. I am running tube props not bar. It does run on Dynatrac rock 60 (dana 60's) now but did have RR axles originally. I'll post a pic so you can see!

cheers

Mark.

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It's an "HGM Automotive Electronics" "Compushift." HGM

You program in diff & transfer ratios; it has throttle position and engine speed input.

You can set all the shift points by speed or rpm, adjust shift pressure, adjust torque covertor lock up.

Have full manual, semi auto, full auto shifts.

It also displays vehicle speed, engine RPM, gear selection, battery volts, whether the torque covertor is locked, gearbox oil temp and pressure and throttle position.

It does a lot more that I don't understand use see the 125 page manual in the link!!

Mark

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