Re: [MV] 1/4 T Overdrive

T. Hintopoulos (hint@northnet.org)
Fri, 10 Sep 1999 10:43:56

Went back to some of my notes on the Warn now Advance Adapters OverDrive
add-on.

Hope this isn't to late.

The OD Ratio: .75:1.
Reduces engine and transmission RPM BUT the transfer case and axles run at the
same speed as before. The speedometer does not have to be changed. It is
connected to the output rear shaft of the transfer case.

The OD is a syncromesh unit, so shifting is easy. With my M38 stock motor,
I can cruise 50-55, but shift out of OD on hills.

I do like this OD unit.

If you are into it, the OD can handle bigger motors, Chevy 283, type. I
wouldn't go larger.

The MB/GPW used the Spicer 18 transfer case with a 27 Tooth Drive Gear.
Warn did not make an OD to fit this configuration.
The intermediate shaft and intermediate gear+rollers bore is 3/4" D.
Ratios: 1:1 and 1.97:1

The M-38, M38-A1,CJ2A,CJ3A+B and used the Spicer 18 as well BUT with a 26
Tooth Drive Gear.
The intermediate shaft and gear+rollers is 1 1/8" D.
Ratios: 1:1 and 2.43/2.46:1 (depending on where you read it).

The CJ5 used the 29 Tooth Drive gear, with 6 or 10 internal splines,
dependent on transmission used. Transfer case is also Spicer 18.
The intermediate shaft and gear+rollers is 1 1/4" D.
Warn had the appropriate parts for these as well.
Ratios: 1:1 and 2.43/2.46:1 (depending on where you read it).

This drive gear is what is bolted to the transmission output shaft. It gets
removed, a special fitting is bolted in its place, then the OD slides
over it. The OD unit has a drive gear on it that mates to the transfer case's
intermediate gear cluster.

>> So.... called AA today and I figures out that they do not have a clue what
>> an MB is (or GPW either). He said it will fit all jeeps from 41 on, that
>> use the T18 transfer case. There are 4 jeep versions, 6 spline and 10
>> spline and 29 tooth and ? tooth (I forgot the other).
>>
>> The key is that 1) he did not know what an MB, or WWII jeep was, and 2) he
>> said they fit from 1941 on. So, if your after one I would open the back PTO
>> cover, count the splines in the tranny main shaft and count the teeth on
the
>> mainshaft gear and give them a call.

I know of some that swapped out the MB/GPW transfer case for a newer one
to install the OD unit. Mine was an M38 application, no change neccessary.

For those that are interested, there was and I think still is, an aftermarket
Tapered Roller Bearing intermediate shaft kit for the later 1 1/8 and 1 1/4" D
shafts. It does away with the old rollers and places tapered bearings in
the ends of the new intermediate gear that comes with the kit. You then
shim them to a zero end play fit.

Hope this helps. I purchased both the OD (Warn) and the Intermediate Shaft
Kit (Tapered Bearings) from 4 Wheel Parts Wholesaler, California back around
1980 for my M38.

Hope this helps.
Ted Hintopoulos.

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