5.38 vs 4.88 opinions?

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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5.38 vs 4.88 opinions?

Post by GPW13551 » Fri Apr 25, 2014 7:06 pm

What are the benefits of having 5.38 gearing in a gpw /mb? I just bought a new axle that has stock gearing but currently have 5.38 in the front. I obviously need to change one or the other. I just wanted to know if there is a benefit of the 5.38 over stock.

I'm sure I will rarely attempt to drive over 50 mph.


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Re: 5.38 vs 4.88 opinions?

Post by Joe Gopan » Sat Apr 26, 2014 3:50 am

5.38 has worked fine in the CJ-2A, CJ-3A, CJ-5, and M-38/M-38A1, they do not appear to be over worked. The OEM Basic tire for the 40's-50's CJ's was the 6.00 X 16 NDT style Goodyear All Service. If you have a CJ-2A or CJ-3A with 6.00 X 16 to drive and compare, you will note it takes a bit more revving and clutch slipping to get an MB rolling than it does the CJ or M-38 type due to the higher MB 4.38 Gears.
My preference for the MB would be to stay with the 4.88.
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Re: 5.38 vs 4.88 opinions?

Post by Wolfman » Sat Apr 26, 2014 5:54 am

I agree. Go with the 4.88.
I have a CJ-2a and a GPW and the GPW will run circles around the CJ. and I like it better on the road.
I think the 5.38 was a compromise when the CJ came out because of it's wide range of uses. ( Don't know why they put it in the M-38 unless it was cheaper to make one gear fit all ? )
Willy's was trying to sell the CJ to farmers as a one vehicle do all vehicle. I have seen film clip ads showing farmer John plowing his field with a CJ one day and loading the family up to go to church on Sunday morning. The 5.38 would pull the plow better and still get the clan to the Sunday morning sermon.
Of course, we all know, John Deere and Farmal won the farming battle.
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Re: 5.38 vs 4.88 opinions?

Post by Fred Coldwell » Sat Apr 26, 2014 6:08 am

Hi GPW13551:

In addition to the lower (numerically higher) axle ratio of 5.38, the CJ-2A and the later jeeps listed by Ben Dover also had a lower (numerically higher) low range gear ratio in the transfer case, 2.43 vs 1.97 for the MB/GPW. These lower gear ratios made farm plowing and towing heavy loads easier for the CJ-2A and gave it higher torque at lower road speeds. So which axle ratio is best for you probably depends on your intended use. If you're just going to be driving around town locally in your GPW getting bread and milk well under 50 mph, then the 4.88 ratio should be fine.

If you are going to be in a lot of parades behind people marching on foot, the 5.38s might suit you better as your be able to "idle along" as bit slower than with the 4.88s. The combined overall lowest gear ratio of a GPW in first gear low range is 25.620 while a CJ-2A is 36.579, roughly a 2 to 3 difference. A CJ-2A with 5.38 axles and the transfer case 2.43 low range engaged will go 2.2 mph at 1,000 rpm, 2.7 mph at 1200 rpm, and perhaps 1.7 mph at 800 rpm. Increasing those "idle along" speeds by 50% for a stock GPW (the same as dividing the CJ-2A road speeds by 0.67%) gives a stock GPW "idle along" speeds of 3.3 mph at 1,000 rpm, 4.0 mph at 1200 rpm and 2.5 mph at 800 rpm. People walking briskly can go 3.0 miles in one hour, but parades tend to stop and go in fits and starts. So the lower the overall gear ratio in a parade vehicle the slower it can idle along and the fewer times you have to push in the clutch to avoid running over those in front of you. But the GPW 5.38/1.97 combo will still have you pushing in the clutch often during parades, so selecting the 5.38s while keeping the 1.97 transfer case low range solely for parades may not, in the end, help you slow down enough to make a useful difference.

If you plan on doing a lot of off-road trail riding, the 5.38s with the GPW 1.97 transfer case low range gear ratio will be marginally better than the stock 4.88/1.97 combo due to slightly slower speeds and slightly better gradeability. But for bread and milk runs stay with the 4.88s to keep the milk cold during a quicker trips back home. I hope this helps you make an informed choice. :D
Happy Jeep Trails,

Fred Coldwell
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1945 CJ2-26 - X50
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Re: 5.38 vs 4.88 opinions?

Post by Marty, SoCal » Sat Apr 26, 2014 6:09 am

M38's have 700-16 tires, the high range gearing is pretty close to the GPW once you figure in the larger tires. The larger tires offer better floatation.
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Re: 5.38 vs 4.88 opinions?

Post by andys » Sat Apr 26, 2014 4:05 pm

I previously restored a '46 cj2a, and it had the stock 5.38 gears. I found that without an overdrive it always felt like the engine was straining while I was cruising around at about 50mph.

Before I tore my gpw down for the restoration, I took it for a few drives and found it cruised at a noticeably easier rpm. Not a big difference in gear ratio by the numbers, but made a big difference in comfort, in my opinion.

Funny thing, when I disassembled the front axle, I found that 5 of the 6 bolts holding on the passenger side spindle were stripped... So much for 50 mph :shock:

Regards, Andy

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Re: 5.38 vs 4.88 opinions?

Post by GPW13551 » Sat Apr 26, 2014 6:18 pm

Thank for all of the input. I'll be going with stock gearing.

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Re: 5.38 vs 4.88 opinions?

Post by rondo » Tue Apr 29, 2014 8:09 am

I would go with the 5.38 for parades but Mr. Coldwell has it absolutely correct. I've only been in 1 parade but it was really painful clutching so often. I don't think I would take my jeep 50? haha seems to be happy at 40 and unhappy at 41.
I suppose if parades are important there is an aftermarket kit from Tera manufacturing for a 3:15 low range kit. this is from their site:
Changing the transfer case gears from 2.03 to 3.15 has the same effect in low range as changing from 3.54 to 5.38 gears while leaving high range unchanged for good freeway driving. Changing from a 2.46: low range to 3.15 is nearly the same as going from 4.56 to 5.38 gears. Three digit crawl ratios are possible with the use of a compound low type transmission such as a T-18, the Tera 3.15 gear set and 5.38 axle gears. A very respectable 51:1 crawl ratio is the result of using the Tera 3.15 gear set in an early CJ with 5.38 gears and a three speed transmission.
note that early dana 18s will not work with these gears. I don't suppose too many peeps want to replace their ww2 tcase just for parades. Being a 4wheeler myself we replace transfer cases in our sleep :)
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Re: 5.38 vs 4.88 opinions?

Post by Joe Gopan » Tue Apr 29, 2014 8:18 am

There are times when the MB/GPW Jeep is not a good parade Jeep because of the 4.88 Ratio.
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Re: 5.38 vs 4.88 opinions?

Post by Chuck Lutz » Tue Apr 29, 2014 8:32 am

I go with my GPW in LOW range on the transfer case and it does just fine at our parades with only minimal clutching and it would not matter what gears I had in it when the parade comes to a dead STOP on occasions. We run quite a few MVs as a group but our rate of progress is determined by the groups ahead of us so gearing with 5.38s would not really help much and would put that much more strain on the driveline during the 35 miles or so of backroads to get there and to drive back home.

Hey...as long as the axles don't leak, make a lot of noise and generally WORK as they are supposed to...no need to mess with them on my jeep!
Chuck Lutz

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Re: 5.38 vs 4.88 opinions?

Post by Joe Gopan » Thu Mar 22, 2018 3:20 pm

This is one of the few times I would endorse free wheeling hubs. Use precaution in LO Range, tho, as one can snap an MB/GPW rear axle if the clutch is let out too fast.
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Re: 5.38 vs 4.88 opinions?

Post by harve » Sat Mar 24, 2018 4:13 am

4.88 cross country. 5.38 Farm use , I love this hobby

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Re: 5.38 vs 4.88 opinions?

Post by Joe Gopan » Sat Mar 24, 2018 4:49 am

And this is why I choose my M-338A1 over my MB for certain parade routes.
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Re: 5.38 vs 4.88 opinions?

Post by Joe Gopan » Sat Mar 24, 2018 5:10 am

The M-38A1 can still be a speed demon, mine will wind the speedometer needle all the way past 60 and back to zero.
I would not recommend this for average M-38A1 owners, especially those whose Jeeps are not maintained in 100% factory condition.
I only tried this every 2 or three years for the first 35 years. Did it for those who claimed Jeeps would not go faster than 40MPH.
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Re: 5.38 vs 4.88 opinions?

Post by dinof » Sat Mar 24, 2018 6:14 am

Just disconnect the front driveshaft and your parade ready.

My vote is to stick with the 4:88. 5:38 to low. I had 5:38's in my other jeep 40 years ago.
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