Rear End Question

[tagroff]

I have a 1928 RPU I think it has a 4:11 rearend I would like to go to something like a 3:78 to help ease the engine strain when cruising down the road ..Am I right in assuming it has a 4:11..If so how hard is it to change this gear out to a 3:78...Thanks a head of time for your help

[30 Closed Cab PU]

Some info in this string, at least on my 30 ccpu looks like it is fairly sinple. Change the diff gear, and change the turtle on the speedometer so the speedometer reads correctly.


I am considering changing to a 3.54 with a standard head, may consider going to a higher compression head.


Not sure if this info is completely accurate for a 28.


https://www.fordbarn.com/forum/showthread.php?t=252019

[100IH]

Some pickups had 4.11 gears, but that is a minority. Pickup is very light veh., might consider one notch taller than std ratio.

[SSsssteamer]

[QUOTE=30 Closed Cab PU;1688869] I am considering changing to a 3.54 with a standard head, may consider going to a higher compression head.



Ditto for me. The right idea! 3.54 gearing has worked well for me in my stock '29 Tudor. My '31 CCPU worked well with 3.27 gears and also using a higher compression head. An amazing improvement.

[Charlie Stephens]

I have 3.54 gears in my '31 RDPU and like them. I have 3.78 gears in my '32 roadster and wish they were also 3.54 but it is not worth the trouble to change them.

Charlie Stephens

[Tom Wesenberg]

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Some 1928 drive shafts may not accept the later ring and pinion. You might need to find a complete rear end. I plan to use 3.27 ratio gears in my spare rear.

[30 Closed Cab PU]

[QUOTE=SSsssteamer;1688883]

Originally Posted by 30 Closed Cab PU

I am considering changing to a 3.54 with a standard head, may consider going to a higher compression head.



Ditto for me. The right idea! 3.54 gearing has worked well for me in my stock '29 Tudor. My '31 CCPU worked well with 3.27 gears and also using a higher compression head. An amazing improvement.

I like your trucks, have not one painted white before, must be work to keep it clean. What is on the door of the black one?


Thanks for your results of changing the diff and head. With your info, think I will go with the 3:54 and standard head that is on it. Looked at pricing on the parts - do not want the added cost of changing heads, plus am trying to keep the existing patina of the truck as is.

[Purdy Swoft]

Light colors , especially white , shows dirt less than the darker colors. A higher compression head will give the most noticeable improvement in power that you can actually feel !!!

[30 Closed Cab PU]

Originally Posted by Purdy Swoft

Light colors , especially white , shows dirt less than the darker colors. A higher compression head will give the most noticeable improvement in power that you can actually feel !!!

Hope Thanks Purdy, I do not mean to hijack the thread. Figure if I am not happy with the power, wait till another time to change/upgrade the head. Am not experienced, but seems it is just check/grind the new head and add the new head with a new head gasket. Just do not have the $$$ now to change diff and head.

[Terry, NJ]

Well! I spent last winter rebuilding a blown 3.78 rear and I went to a 3.54 gear set, Pricey! Abt $700. I'm glad I did! The car is vastly improved over the 3.78. I'd recommend it to anyone. 4.11 gears! What are they good for? I had that type of gearing in my 46 merc. I hated it!My car has a good engine, possibly an HC head. Mod B carb and a bored out A manifold. It runs good! My only regret is that I didn't get a 3.27. By the way, if you're still stuck on 3.78 gears, I have a set i want $40 For. Are the worn, Probably! but I think there's a lot of life in them. Properly set up, with new bearings, I think they'll work fine for you.
Terry

Originally Posted by tagroff

I have a 1928 RPU I think it has a 4:11 rearend I would like to go to something like a 3:78 to help ease the engine strain when cruising down the road ..Am I right in assuming it has a 4:11..If so how hard is it to change this gear out to a 3:78...Thanks a head of time for your help

[Terry, NJ]

I unintentionally ignored part of your question. It is about a major a job as you'll probably do on a model A, short of rebuilding the engine. You must have or borrow a torque wrench that reads in inch lbs. You will need to have or borrow a fixture to hold the trumpets while you're assembling the gears. two pcs of 2X4 will suffice with clamping bolts. I could go on, but I think you get the picture. If it was easy, everyone would do it, And I merely broke the surface. You'll need infinite amounts of patience. The rear must be assembled, taken apart, and reassembled more than once or twice. There are ten bolts around the trumpets/axle housings. I found you can get away with only using five. It's quite a job, but it's do able!
Terry

Originally Posted by tagroff

I have a 1928 RPU I think it has a 4:11 rearend I would like to go to something like a 3:78 to help ease the engine strain when cruising down the road ..Am I right in assuming it has a 4:11..If so how hard is it to change this gear out to a 3:78...Thanks a head of time for your help

[SSsssteamer]

30 closedcab PU,
My '31 Pickup is painted its original color that it was sold new with: Gull Grey. Yes it looks very light in the photo. On the door of the '30 black pickup is a sign that says Gateway Golf Course.