Differential Gearing

[AN/GRC-46]

I know that most of you will recommend against this but I really can't see any downside.

I have the stock 5.83 gearsets front and rear. I also found one set of 4.89 gears. I have the idea of installing the 4.89 in the rear for general road travel. I personally can't see any reason why I would ever need 4WD. However, if I did use 4WD it would be only in slippery conditions such a loose dirt or mud.

I know that driving the wheels at different speeds isn't recommended and is probably dangerous on the road but would it really hurt at a maximum of maybe 5 MPH in 1st or low 1st in dirt/mud?

 

[Angus1]

Yes it really would hurt. Its called "drive line wind up" and it will break stuff.

 

[rosco]

If your on slippery stuff, one end will be pushing, the other pulling. They will try to swap ends of the vehicle. Even different sized tires can cause problems, but there is a lot of jump, between those two ratios.

Lee in Alaska

 

[AN/GRC-46]

Angus1 - would you explain "drive line wind up" and how it would be working in this situation (2WD)?

rosco - I understand that the rear would be pushing more than the front is pulling, but at MAX 5 MPH how much affect would this have, especially when both ends would be slipping anyway.

Remember, this would be operated in 2WD 99.99% of the time, with a max of maybe 3-5 minutes a year in 4WD if I got stuck somewhere (I don't have any plans to drive off-road, ever).

 

[gringeltaube]

I know that driving the wheels at different speeds isn't recommended and is probably dangerous on the road but would it really hurt at a maximum of maybe 5 MPH in 1st or low 1st in dirt/mud?

No problem on slippery surfaces, just a little less effective.
4WD (or 6WD) engaged on firm ground on vehicles w/o central differential should be avoided anyways, even with matched gear ratios!

G.

 

[DDoyle]

RE: Re: Differential Gearing

There is a tendency for people "visiting" our vehicles at car shows, etc. to move every lever on the truck. Hence, if I were contemplating chainging the rear end gearing, I'd also pull the front driveshaft. Then, if the front wheel drive were engaged, there would be no concern anyhow.

Who knows, maybe by winter you'll find another gear set.

Regards,
David

 

[Hm2klie]

RE: Re: Differential Gearing

I have done many gear swaps in jeep CJ5s and I believe that it is Imperitive that you match your ratios. Even if you only drive in 4wd in slippery conditions your rear will tires will spin faster than your front. In mud, sand or snow this WILL cause damage to your transmission, transfer case and will increase the risk of breaking drive shafts. The damage is caused by the truck fighting itself as it is bogged down in mud ect. If the truck were to regain traction suddenly your vehicle would grenade!!!! If you replace only the rear pull your front drive shaft untill you can match ratios. In 2wd you will not cause any damage but pulling the drive shaft will prevent you from trying out 4wd to see what would happen. I repeat this will cause damage read expensive damage. I am just trying to save you some cash. Good luck Drew

 

[gringeltaube]

Re: RE: Re: Differential Gearing

.... In mud, sand or snow this WILL cause damage to your transmission, transfer case and will increase the risk of breaking drive shafts....

...but always depending on brain, right foot weight and lots of other factors!
(BTW: you can easily make your 4x4 "grenade" even with perfectly matched ratios...I know how ... )

 

[SasquatchSanta]

RE: Re: RE: Re: Differential Gearing

This is absolutely absurd!

I don't slight AN/GRC-46 for asking --- that's what forums are for but for anyone to suggest that it could be even boarderline OK is absurd.

I've got an M-37 that has a fresh set of 489s and lockers front and rear. I installed the rear gearing one year and the front the next and even though I have spin-out hubs I removed the front drive shaft when the rears went in and didn't re-install it until the front gears where installed.

 

[gringeltaube]

I repeat my answer to his original question "....but would it really hurt at a maximum of maybe 5 MPH in 1st or low 1st in dirt/mud?" : NO, depending on....

It is clear that the rears will be slipping almost 20% (!) before the front axle starts helping to get him unstuck... not nice, but better than nothing!

I'm NOT recommending this!

G.