Posted by Torvald [172.71.147.38] on Saturday, December 16, 2023 at 00:24:18 :
Greetings,
Back in November I posted a request for info on what lubricant to run in the �after type� transmission of a FFPW. After reading the replies and running several tests of my own I thought I�d put together the results for y�all.
I have a �51� FFPW with the after type transmission, which is the later of the two spur gear transmissions for the FFPW. The transmission has all new bearing assemblies and needles, and clearances/backlash were carefully checked, but the countershaft and cluster gear were not replaced. I also rebuilt the transmission top, so the gearshift lever has no slop in it. The differentials have been changed to 4.89. Also, I have changed my Xfer case so that when in high gear the power doesn�t go through the gear sets but instead passes through as in a transmission in top gear. The rear drive shaft is connected to the yoke at the parking brake (left side) rather than the yoke on the right to the rear of the front drive shaft yoke, and I�m using a WC centered rear axle. Doing this prevents a lot of power loss from the Xfer case.
The problem that prompted the request for lubricant info was noise. I finally got the Beast on the road during this past summer and found that the Sta-Lube 80W90 that I initially used resulted in a noisy trany at 60 MPH during the Eastern Washington summer heat (frequently over 100F). My next lubricant was 85W-140; which I found was too thick for the Eastern Washington winter cold (difficult shifting when cold), but quieted the trany significantly. So then I tried 75W-140 which seems to work well at both temperature extremes, giving a transmission that shifts easily and is quiet; even when I miss a shift and grind the gears a bit (I�m still learning) the grind isn�t nearly as bad as with the 80W-90.
To add yet another dimension to the equation; I played a bit with transfer case lubricant too: I started off with 80W-90 in the Xfer case, but changed to 85W-140 when I changed to 85W-140 in the trany, and left it in when I changed to 75W-140 in the trany. I really liked the reduced noise with 75W-140 in the trany and 85W-140 in the Xfer case. However I reasoned that, since I wasn�t transmitting power through the gears of the Xfer case I really didn�t need the high viscosity 85W-140 there and the 80W-90 would have much less drag, so I changed the Xfer case back to 80W-90. I believe it was a good decision as there seems to be a bit more pep to the beast without the drag from the very thick 85W-140 in the transfer case.
To sum it all up: I have 75W-140 in the transmission and 80W-90 in the transfer case. This combination seems to give good noise reduction and ease of shifting in the transmission and lack of drag in the transfer case. Don�t forget the GL-4 designation!
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