76 GMC TH400---dipstick boot, or no??

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

OldBlueDually

Full Access Member
Joined
Jun 8, 2020
Posts
2,395
Reaction score
8,384
Location
Minnesota
First Name
Justin
Truck Year
1976 GMC
Truck Model
C30
Engine Size
455 Olds
Gents, my 76 GMC has an aftermarket (POS) chrome dipstick tube in it. It has an o-ring at the end of it.

It will not fit in the trans properly, because the o-ring groove in the dipstick tube is like it should be on half of it, and very shallow on the other half making the o-ring sit out too far. I sliced one o-ring already, and the one that was on it is also crap.

I called and asked my dad (retired GM mechanic) and he said he thought the 400's had a boot that the dipstick tube goes into. Is this true?

I had a smaller diameter (cross section) o-ring on there, but it leaks fluid. I thought about siliconing the damned thing in!!! I want it right however.

What do you guys suggest? Thanks!!!
 

OldBlueDually

Full Access Member
Joined
Jun 8, 2020
Posts
2,395
Reaction score
8,384
Location
Minnesota
First Name
Justin
Truck Year
1976 GMC
Truck Model
C30
Engine Size
455 Olds
So the 400 in my truck should have a boot?
 

78C10BigTen

Full Access Member
Joined
Apr 12, 2017
Posts
15,562
Reaction score
23,949
Location
pennsylvannia
First Name
Ted
Truck Year
1978
Truck Model
C10 BIG TEN
Engine Size
350
My th350 has the boot style....
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,342
Reaction score
3,584
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
Every transmission used the o-ring style dipstick prior to the late 70s, after that GM went to the much better barrel design.

I know for a fact (last time I bought one was about a year ago) Coan sells a dipstick and tube that uses the barrel seal, has a locking dipstick, and is made of pretty thick steel. It fit very well.
 

OldBlueDually

Full Access Member
Joined
Jun 8, 2020
Posts
2,395
Reaction score
8,384
Location
Minnesota
First Name
Justin
Truck Year
1976 GMC
Truck Model
C30
Engine Size
455 Olds
Thanks for that info Matt, I will check them out too! I was hoping to "stumble" upon an original one to throw in here...
 

Dave M

Banned
Joined
Jul 30, 2019
Posts
602
Reaction score
1,305
Location
Australia
First Name
Dave
Truck Year
1976
Truck Model
C10
Engine Size
454
As Matt mentioned, the boot type is much better, I used a Proform item with the locking dipstick, works great.
 

Latest posts

Forum statistics

Threads
42,030
Posts
907,730
Members
33,523
Latest member
BigRed82k20
Top